EP2815421B1 - Method for producing iii-n templates and the reprocessing thereof and iii-n template - Google Patents

Description

The present invention relates to processes for the preparation of composite substrates (hereinafter referred to as "template (s)") and to the production of III-N single crystals. The processes according to the invention make it possible to produce crack-free III-N single crystals, which are particularly suitable for use as wafers. III means at least one element of the third main group of the periodic table selected from the group of Al, Ga and In.

III-N single crystals are of great technical importance. These materials are based on a large number of semiconductor components and optical-electrical components such as power components, high-frequency components, light-emitting diodes and lasers. In the production of such devices, epitaxial crystal growth is often carried out on a starting substrate, or a template is initially formed on a starting substrate, whereupon III-N layers or single crystal bodies can subsequently be deposited by further epitaxial growth. As starting substrates III-N substrates or in particular foreign substrates can be used. When using foreign substrates, strain and cracking within a III-N layer may occur during growth due to differences in the thermal expansion coefficients of the starting substrate and the grown layer. Thicker layers can also be grown with the aid of partially structured, deposited in an external process intermediate layers of WSiN, TiN or SiO ₂ and are subsequently detached as free-standing layers, which typically have plastic, concave bent c-lattice planes and surfaces. At and above the interface between the starting substrate and the grown III-N layer, vertical and horizontal microcracks may develop that may expand with time and lead to breakage of the GaN layer during or after the cooling process.

From studies of Hearne et al., Applied Physics Letters 74, 356-358 (1999 ) it is known that during the deposition of GaN on sapphire substrate an increasing with the growth of increasing tensile stress (stress) builds up. In situ stress monitoring revealed that the tensile strain generated by the growth can not be relaxed by annealing or thermal cycling. This means, inter alia, that a strain obtained at the end of growth of the GaN layer again assumes the same value after cooling and reheating to the same (growth) temperature. In Hearne et al. One also finds an explanation of the background, context and possibilities of observation of extrinsic (namely generated by different thermal expansion coefficients between sapphire substrate and GaN layer) and instrinsischer (namely generated by growth) tension (stress).

To counteract the generation of stress, namely tensile stress, in multilayer constructions of III-N layers on foreign substrates, with increasing growth of the III-N layer structures, in the US 2008/0217645 A1 Firstly, an AlGaN gradient layer is applied to a nucleation layer, and second, relaxed GaAl (In) N interlayers are sandwiched between nitride layers.
Furthermore, in the US 2008/0217645 A1 For example, if, after multiple epitaxial layers, the dislocation density in the epitaxial layer construction excessively increases, mask layers with, for example, SiN, MgN, and / or BN masking material are employed to reduce the dislocation density.
Also in further examples and other contexts the influence of mask layers on the change of the dislocation density is described, for example at Tanaka et al., Jpn. J. Appl. Phys. Vol. 39, L831-L834 (2000 ) (particularly with respect to the use of a SiC foreign substrate) in which WO2012035135A1 (in particular with respect to the use of a Si foreign substrate) and in the publication by Hertkorn et al. discussed in more detail below. (2008).

In Journal of Crystal Growth 289, 445-449 (2006 ) is described by Napierala et al. described a method of making GaN / sapphire templates on which crack-free thin GaN layers are grown by controlling the intrinsic strain in gallium nitride by adjusting the density of gallium nitride crystallites so that strains in the thin layers can be released by bending , However, thick layers in this process can not compensate for the pressure during growth and tend to bend despite the bending Fractures. Richter et al. (E. Richter, U.Zeimer, S.Hagedorn, M.Wagner, F.Brunner, M.Weyers, G.Tränkle, Journal of Crystal Growth 312, [2010] 2537 describe a method for producing GaN crystals via hydride vapor phase epitaxy (HVPE), in which GaN layers of 2.6 mm can be grown crack-free by adjusting the partial gallium chloride pressure, the resulting GaN layers having on the surface a multiplicity of V Have pits. A crystal grown with this process has a thickness of 5.8 mm, but it has longer cracks. In Journal of Crystal Growth 298, 202-206 (2007 ) Brunner et al. the influence of the layer thickness on the curvature of the growing III-N layer on. The growth of GaN and AlGaN, possibly with an InGaN compliance layer, on GaN sapphire template is investigated. It has been found that for GaN and AlGaN with 2.8% and 7.6% Al mole fraction, the concave curvature increases during growth. Furthermore, the concave curvature increases with increasing aluminum content. In addition, the influence of an Si-doped indium-gallium nitride layer on the growth of an AlGaN layer of 7.6% Al mole fraction on a GaN buffer layer is shown. For this purpose, on the one hand an AlGaN layer with 7.6% Al mole fraction is grown directly on a GaN buffer layer and on the other hand, a Si-doped indium-gallium nitride layer as an intermediate layer on a GaN buffer layer, wherein subsequently an AlGaN layer with 7.6% Al-mole fraction is grown on the intermediate layer. Thus, it has been shown that applying an Si-doped indium-gallium nitride layer to a GaN buffer layer results in compressive stress in the crystal. During this process, the initial concave curvature of the GaN buffer layer is converted into a slightly convex curvature as the temperature is lowered, and by growing an In _0.06 Ga _0.94 N layer within the same process, this convex curvature increases as it continues to grow. The subsequent application of an Al _0.076 Ga _0.924 N layer on this In _0.06 Ga _0.94 N layer finally achieves a concave curvature that is comparatively less than the resulting curvature without In _0.06 Ga _0.94 N interlayer.

E. Richter, M. Founder, B. Schineller, F. Brunner, U. Zeimer, C. Netzel, M. Weyers and G. Tränkle (Phys.Status Solidi C 8, No. 5 (2011) 1450 ) describe a method for producing GaN crystals by means of HVPE, wherein a thickness of up to 6.3 mm can be achieved. These crystals have sloped sidewalls and V-pits on the surface. Furthermore, a concave curvature of approx. 5.4 m and a dislocation density of 6x10 ⁵ cm ^-2 can be seen in the crystal lattice.

Hertkorn et al. describe in J. Cryst. Growth 310 (2008), 4867-4870 Process condition for forming 2-3μm thin GaN layers by metal organic vapor phase epitaxy (MOVPE, Metal-Organic Vapor Phase Epitaxy) using in situ deposited SiN _x masks. With regard to different positions of the SiN _x masks, specifically at 0 (ie directly on an AlN nucleation layer) or after the growth of 15, 50, 100, 350 and 1000 nm, the connection with a possible influence on defects becomes or the course of the dislocation density examined. As a result, it is considered that defect dislocation reduction is most effective when the SiN _{x is positioned} after the growth of 100nm GaN. On the other hand, however, it is highlighted as negative and problematic that the SiN _x deposition directly on or near the AlN nucleation layer produced highly compressively strained GaN layers and for layering - so-called stacking faults visible in the transmission electron microscope and further led to a broadening of the D ⁰ X line width and the X-ray peaks - and therefore to avoid such problems a second SiN _x mask was deposited after 1.5 μm for the purpose of shielding the defects. Apart from a reduction in the dislocation density, which was also described as associated with adverse effects, the authors did not recognize which parameters important for the re-use of templates are influenced by a SiN _x deposition and, above all, whether and how a later tendency to crack can be suppressed in the growth of further III-N layers and massive crystals.

DE 102006008929 A1 describes a nitride semiconductor device based on a silicon substrate and its manufacture, with the deposition of an aluminum-containing Nitridankeimschicht on the silicon substrate. A process is described which is based specifically on the use of a silicon substrate, wherein it is found that the growth of semiconductor layers on sapphire substrates is subject to completely different boundary conditions than the growth on silicon substrate. In fact, in the result is the according to the system of DE 102006008929 A1 grown III-N layer after cooling to room temperature is not compressive, not even compressed almost compressively, but merely less tensilely braced than a conventional grown on silicon substrate III-N layer.

US 2009/0092815 A1 describes the production of aluminum nitride crystals between 1 and 2 mm thick and aluminum nitride layers of 5 mm thickness. These layers are described as crack-free and can be used to cut colorless and optically transparent wafers with more than 90% usable area for use in device fabrication or device fabrication.

EP 1 501 117 A1 discloses a method of growing dislocation and defect poor GaN crystals using an epitaxial lateral overgrowth (ELO) mask and a so-called defectseeding mask of Pt, Ni or Ti together. In particular, the deposition of an ELO mask of SiN or SiO 2 on a sapphire substrate with subsequent GaN growth is described.

WO 2007/068756 A1 describes a method for producing low dislocation density GaN. In particular, a so-called universal-lateral-overgrowth method is presented which, in principle, even without a mask and only by adaptation of 3D and 2D growth parameters leads to a reduction of threading dislocations and bending-poor and crack-free GaN layers.

US 2003/0232457 A1 discloses a GaN template using an AlGaN intermediate layer between a sapphire substrate and a GaN layer and adjusting a compressive strain.

Klein et al., Journal of Crystal Growth 324, 63-72 (2011 ) describe a method of making a template comprising a sapphire substrate and at least one Al _0.2 Ga _0.8 N crystal layer, wherein a SiN _x interlayer is at a distance from the foreign substrate or AlN nucleation layer formed thereon 150 nm or 170 nm is applied; the SiN _x interlayer to reduce the dislocation density in order to achieve a gradual transition from the sapphire (Al ₂ O ₃₎ to the desired -Gitterkonstante different lattice constant and continuous voltage adapted to the purpose.

Krost et al., Applied Physics Letter 97 (No. 18), 181105-181105 (2010 ) describe a method for producing a layer structure with nucleation layer, 130 nm AlGaN layer, first in situ SiN mask, 1.6 μm GaN buffer layer, 15 nm low temperature AlN interlayer, second in situ SiN mask, 1.6 μm GaN Buffer layer and Bragg layers. Thus, the distance of the first in-situ SiN mask from the AlN nucleation layer formed on the substrate should be 130 nm.

Krost et al., (Journal of Crystal Growth 275 (2005), pp. 209-216) ) describes the in situ curvature measurement for determining the strain profile during the MOVPE growth of III-N layers. As the substrate, Si was mainly used.

The processes of the above-described prior art have in common that after growth and cooling, III-N crystals are obtained, which are exposed to strong extrinsic and intrinsic stress, which can cause cracks or other material defects, which may increase the material quality and processability to III-N Restrict substrates.

Therefore, it was an object of the present invention to provide template and III-N crystal preparation methods that enable III-N crystals to grow under conditions that minimize the inclusion of material defects and improve crystal quality and processability.

This object is achieved by a method according to claim 1. Further developments are specified in the corresponding subclaims. Furthermore, the invention provides a method according to Claim 10 and a new template according to claim 11 ready. Useful uses are defined in claims 13 and 14.

According to the invention, in a template (ie a unit comprising sapphire-comprising foreign substrate and a relatively thin III-N crystal layer, such a template unit itself being used as the starting product for the subsequent production of III-N crystal boules / ingots or of III-N- Components function) the correct influencing of the critical parameters curvature and strain of the template in each case alternatively recognized as particularly important for advantageous properties of the template and its further use. It has surprisingly been found that these parameters can be very favorably influenced by carefully selected factors, which include in particular the provision and layering of a masking material depending on the position or layer position in the template, whereby especially a later crack formation using the template according to the invention is effective can be counteracted. In accordance with alternative technical solutions, it is necessary to ensure that the curvature adjustments that are relevant to the invention and that are favorable for the further use of the template are (i) that a curvature difference (K _a -K _e ) to be specified later in at least one growth phase during template production Range ≥ 0, and more preferably> 0, or (ii) that the template prepared is substantially non-curved or negatively (convexly) curved in the state of growth. According to the invention, it is possible to produce templates which have no or almost no curvature or a negative curvature and thus only a low intrinsic stress under epitaxial crystal growth conditions, which has proven to be advantageous as a starting point for further processing. As experimentally shown, it is possible according to the invention that the aforementioned technical solutions (i) and (ii) can advantageously be realized without inclusion of dopants in the III-N layer of the template, ie that apart from the components for the mask material intermediate layer no Foreign components are provided in the template ("foreign" in the sense of other than the III and N components of the III-N layer). Since, according to the invention, it can be ensured that the formation of the III-N layer of the template takes place in situ with the formation of the mask material intermediate layer, the abovementioned technical solutions (i) and (ii) can also be realized independently of surface structuring of the sapphire substrate provided ; Namely, the latter concerns only conventional ex situ patterns, such as opening windows, forming stripes or dots, and other mask structures, such as by (photo) lithography, ie conventional cases in which the desired curvature behavior is not as in the invention can be adjusted.

In the case of such optionally provided surface structuring of the sapphire substrate itself, which may optionally have mask patterns, it is further ensured according to the invention, in addition mask material as an intermediate layer at least partially directly on the sapphire substrate or the optionally present III-N nucleation layer thereon (ie immediately adjacent), or in the crystalline III-N material of the template at an appropriate distance from the major surface of the sapphire substrate or the optional III-N nucleation layer thereon (ie, where contact with substrate or III-N nucleation layer takes place), even if optional Surface structures are provided on the sapphire substrate. In addition, the dimensions are different: surface masking and patterns performed ex situ typically have a thickness dimension in the micron range, whereas the in situ masking material intermediate layer relevant to the invention typically has a thickness dimension in the sub-micron range.

According to the invention, it is possible to set a voltage selectively and, if desired, in a specific voltage value which is favorable for further processing; In particular, according to the invention, it is possible to turn a template into a tension-free, optionally even compressively tensioned region. This may be accomplished in a preferred embodiment solely by the provision of a masking material interlayer as described herein.

The process according to the invention, and to a greater extent the observance of the preferred features of the process according to the invention, accordingly permits an advantageous adjustment of the strain in the III-N crystal layer of the template with a value ε _xx at room temperature (alternatively, or additionally, at a growth temperature ) of ε _xx ≤0 and especially ε _xx <0, and, furthermore, of particularly suitable negative ε _xx values, which has a very favorable effect on the inventive re-use of the template and thus represents an alternative feature of the product of the template according to the invention.

Conventional and commonly used pertinent methods have hitherto shown a different behavior or have not recognized the useful correlations recognized here. For example, in conventional methods using the standard sapphire substrate, due to differential thermal expansion coefficients of the foreign substrate and III-N layer and other factors at growth temperature, a concave curvature of the growth surface typically forms in the course of further crystal growth, that is, increasing thickness the III-N layer, continues to increase. Surprisingly, the inventive method can be designed so that during a given growth phase of the III-N material layer of the template noticeably decreases a given curvature despite the further growth of the III-N material layer.
Furthermore, in conventional methods due to a steadily increasing curvature, a correspondingly increasing intrinsic - typically tensile - stress is built up within the crystal, which may already during further growth and in particular further use or processing of the template, at the latest on cooling from the epitaxial growth temperature, easily lead to microcracks and even fractures. In contrast, in the process of the present invention, a controlled intrinsic - typically compressive - stress in epitaxial crystal growth can be selectively controlled or a curvature can be set to zero or nearly zero, so that during the subsequent growth of III-N crystals, eg III-N solid crystals - optionally during continued growth without growth interruption, or as part of a separate growth process with interruption - and even during final cooling, cracks can be avoided.

In such a III-N crystal is further avoided that cracks occur, which limits the material quality and / or the processability to III-N substrates. "Crack-free III-N crystal" according to the present invention means that it has no crack on an area of 15 cm ² when viewed every 30 mm ² image sections with an optical microscope.

wobei a die tatsächliche Gitterkonstante im Kristall und a₀ die theoretisch ideale Gitterkonstante darstellt, wobei für a₀ typischerweise ein Literatur-Wert von a0 = 3.18926±0.00004Å (nach V. Darakchieva, B. Monemar, A. Usui, M. Saenger, M. Schubert, Journal of Crystal Growth 310 (2008) 959-965 ) angenommen wird.
Demgemäß kann durch Aufwachsen von Kristallschichten unter extrinsischem Stress auf die tatsächlich vorliegenden Kristallgitterkonstanten Einfluss genommen werden. Beispielsweise kann durch extrinsischen Stress eine kompressive Spannung auf den wachsenden Kristall übertragen werden, wodurch Gitterkonstanten gegenüber Wachstum ohne Stress verkürzt werden. Dadurch baut sich innerhalb des Kristalls steuerbar und gezielt intrinsischer Stress auf, der die zuvor genannten Eigenschaften Deformation und Verspannung günstig beeinflusst.
Erfindungsgemäß ist es bevorzugt, dass III-N-Kristalle von Templaten der vorliegenden Erfindung einen ε_xx-Wert von ≤ 0, weiter bevorzugt von < 0 aufweisen. Solche Template eignen sich hervorragend als Ausgangsprodukte für das Aufwachsen weiterer epitaxialer Schichten des III-N-Systems, insbesondere zum Herstellen von dicken III-N-Schichten und -Boules (Massivkristalle).Further, according to the present invention, the microscopic property of the deformation ε _{xx of} the lattice constant a can be influenced. The deformation ε is generally referred to in mechanics as a strain tensor , where ε _{xx means} its first component.
For crystal lattices, the deformation ε _xx is defined as follows: $${\epsilon }_{\mathrm{XX}}=\frac{\mathrm{Lattice\; constant\; a}-{\mathrm{Lattice\; constant\; a}}_0}{{\mathrm{Lattice\; constant\; a}}_0}$$

where a represents the actual lattice constant in the crystal and a ₀ the theoretically ideal lattice constant, where for a ₀ typically a literature value of a0 = 3.18926 ± 0.00004Å (acc V. Darakchieva, B. Monemar, A. Usui, M. Saenger, M. Schubert, Journal of Crystal Growth 310 (2008) 959-965 ) Is accepted.
Accordingly, by growing crystal layers under extrinsic stress, the actual crystal lattice constants actually present can be influenced. For example, a compressive stress can be transmitted to the growing crystal by extrinsic stress, whereby lattice constants are reduced compared to growth without stress. As a result, intrinsic stress builds up within the crystal in a controllable and targeted manner, which favorably influences the aforementioned properties of deformation and stress.
According to the invention, it is preferred that III-N crystals of templates of the present invention have an _εxx value of ≤0, more preferably of <0. Such templates are outstandingly suitable as starting materials for the growth of further epitaxial layers of the III-N system, in particular for producing thick III-N layers and boules (massive crystals).

1. 1. Verfahren zur Herstellung eines Templats, welches ein Substrat und mindestens eine III-N-Kristallschicht umfasst, wobei III mindestens ein Element der dritten Hauptgruppe des Periodensystems, ausgewählt aus Al, Ga und In, bedeutet, wobei das Verfahren die Schritte Bereitstellen eines Substrats und
   Wachstum eines kristallinen III-N-Materials auf dem Substrat
   umfasst, wobei ein Maskenmaterial als Zwischenschicht auf dem Substrat, welches gegebenenfalls eine III-N-Nukleationsschicht aufweist, oder im kristallinen III-N-Material in einem Abstand vom Substrat oder der gegebenenfalls vorgesehenen III-N-Nukleationsschicht abgeschieden wird und danach das Wachstum eines kristallinen III-N-Materials erfolgt oder fortgesetzt wird, wobei der Abstand der Zwischenschicht des Maskenmaterials gegenüber dem Substrat bzw. der gegebenenfalls darauf gebildeten III-N-Nukleationsschicht maximal 50 nm beträgt,
   und wobei, wenn während des Kristallwachstums die Krümmung der Wachstumsoberfläche des III-N-Kristalls zu einem ersten, relativ früheren Zeitpunkt mit K_a und zu einem zweiten relativ späteren Zeitpunkt mit K_e bezeichnet wird, für eine Krümmungsdifferenz (K_a-K_e) ≥ 0 gesorgt wird.
   Bevorzugt ist der Bereich K_a-K_e > 0.
   Das Substrat ist als Fremdsubstrat ausgebildet, d.h. ist ein gegenüber dem III-N-Material des Templats verschiedenes Material, insbesondere umfasst das Fremdsubstrat Saphir oder es besteht aus Saphir.
   Das Maskenmaterial ist geeigneterweise als ein von Substratmaterial und III-N verschiedenes Material definiert, auf dem III-N-Wachstum gehemmt, gestört oder verhindert ist. Beispiele für das Maskenmaterial werden unten näher beschrieben.
   Die Ausdrücke "relativ früh" und "relativ spät" bedeutet ein erster bzw. zweiter Zeitpunkt während des Kristallwachstums, der jeweils Anfang und Ende des gesamten Kristallwachstums der III-N-Kristallschicht sein kann, aber auch nur eine bestimmte Phase des gesamten Kristallwachstums der III-N-Kristallschicht definieren kann und es im letzten Fall nicht darauf ankommt, wie das Krümmungsverhalten vor dem ersten bzw. nach dem zweiten Zeitpunkt ist. Zum Beispiel, ohne aber darauf beschränkt zu sein, ist der relativ frühe erste Zeitpunkt gegeben durch den Zeitpunkt des Aufbringens der Zwischenschicht des Maskenmaterials, und zum Beispiel ist der relativ späte zweite Zeitpunkt gegeben durch das Ende der Herstellungsstufe des Templats, wiederum ohne darauf beschränkt zu sein. Den möglichen Varianten der jeweiligen Zeitpunkte gemeinsam ist eine jeweils günstige Beeinflussung von (Ver-)Spannung im gebildeten III-N-Kristall und/oder vom Krümmungsverhalten bzw. -zustand des Templats bei Wachstumstemperatur und/oder bei Raumtemperatur, jeweils im Vergleich zur Nichtbeachtung der genannten Beziehung K_a-K_e. Der Ausdruck "Zwischenschicht" ist in weitem Sinne zu verstehen, in der Regel als eine Materiallage, die Maskenmaterial umfasst, gegebenenfalls neben Maskenmaterial noch weiteres Material wie etwa das III-N-Material umfasst oder materialfreie Lücken aufweist. Die Dicke der "Zwischenschicht" ist variabel, ist aber in der Regel dünn bis sehr dünn, geeigneterweise im Nanometer-Bereich (z.B. bis maximal 50 nm, vorzugsweise unter 5 nm) oder im Subnanometer-Bereich (z.B. bis unter 1 nm, insbesondere bis unter einer Monolage, d.h. 0,2 bis 0,3 nm oder weniger).
   Abscheiden des Maskenmaterials der Zwischenschicht "auf dem Substrat" bedeutet direkt angrenzend an eine Oberfläche des Saphirs oder der optionalen III-N-Nukleationsschicht über dem Saphir (nicht erfindungsgemäß), und "in einem Abstand vom Substrat" bezeichnet den Abstand der Lage/Position der Maskenmaterial-Zwischenschicht von dieser Oberfläche.
2. 2. Verfahren gemäß Punkt 1, dadurch gekennzeichnet, dass die Krümmungsdifferenz (K_a-K_e) mindestens 5 km^-1, bevorzugt mindestens 10 km^-1, weiter bevorzugt mindestens 20 km^-1 und insbesondere mindestens 50 km^-1 beträgt.
3. 3. Verfahren gemäß Punkt 1 oder 2, wobei das Templat weiterverwendet wird zum Aufbringen von einer oder mehreren weiteren III-N-Kristallschicht(en), wahlweise zum Herstellen eines III-N-Massivkristalls.
   Weil das hergestellte Templat erfindungsgemäß durch Beachtung der Krümmungsdifferenz K_a-K_e günstig beeinflusst wird ist das weitere Krümmungserhalten der Wachstumsoberfläche des III-N-Kristalls während eines sich optional anschließenden Aufbringens bzw. Aufwachsens weiteren Halbleitermaterials nicht festgelegt.
4. 4. Verfahren zur Herstellung von III-N-Einkristall, wobei III mindestens ein Element der dritten Hauptgruppe des Periodensystems, ausgewählt aus Al, Ga und In, bedeutet, wobei das Verfahren die folgenden Schritte umfasst:
   • aa) Bereitstellen eines Templats, welches ein Saphir umfassendes Fremdsubstrat und eine III-N-Kristallschicht umfasst, wobei das Templat im Bereich einer Wachstumstemperatur nicht oder im wesentlichen nicht gekrümmt ist oder negativ gekrümmt ist, wobei im bereitgestellten Templat im Bereich über dem Fremdsubstrat oder in der III-N-Kristallschicht des Templats ein Maskenmaterial als Zwischenschicht so abgeschieden ist, dass ein Abstand der Zwischenschicht des Maskenmaterials gegenüber dem Substrat bzw. der gegebenenfalls darauf gebildeten III-N-Nukleationsschicht maximal 50 nm beträgt;
   • bb) Durchführen eines epitaxialen Kristallwachstums zum Bilden von weiterem III-N-Kristall auf dem Templat gemäß aa), wahlweise zum Herstellen von III-N-Massivkristall,
   • cc) optional Trennen von III-N-Einkristall oder III-N-Massivkristall und Fremdsubstrat. Erfindungsgemäß ist es bevorzugt, dass die erwünschte günstige Nichtkrümmung oder (kompressive oder konvexe) Negativkrümmung des Templats bei dessen Erhitzen im Anfangszustand, d.h. bevor das weitere Wachstums gemäß Schritt bb) erfolgt, durch gezielte Positionierung einer Zwischenschicht des Maskenmaterials in definierter und begrenzter Höhenlage auf/über dem Fremdsubstrat eingestellt wurde. Hierzu und zum Ausdruck "Zwischenschicht" s. die obigen Punkte 1 und 2.
   Falls diese Maßnahme für die genannte Bedingung nicht oder nicht allein ausreicht, können zusätzlich weitere Parameter beachtet und eingestellt werden, zum Beispiel indem während einer begrenzten Phase des Wachstums der III-N-Schicht des Templats eine Variation der Wachstumstemperatur (Absenkung aufgrund der Wahl von Saphir als Fremdsubstrat) erfolgte und damit ein ergänzender und/oder alternativer Beitrag zu der Beziehung K_a-K_e ≥ 0 geliefert wurde.
   Der Ausdruck "Wachstumstemperatur" bezieht sich auf eine Temperatur, bei der eine Abscheidung, insbesondere ein epitaxiales Wachstum, eines gewünschten III-N-Kristall ermöglicht wird.
5. 5. Verfahren gemäß einem der vorangehenden Punkte, dadurch gekennzeichnet, dass wenn für das Templat als Fremdsubstrat Saphir einer Dicke (d_Saphir) von ungefähr 430µm (d.h. ±20µm) und als III-N-Kristallschicht des GaN einer Dicke (d_GaN) von ungefähr 7 µm (d.h. ±0,5µm) verwendet oder eingestellt wird,
   beim III-N-Kristall eine Krümmung des Templats (K_T) an der Wachstumsoberfläche
   1. (i) bei Wachstumstemperatur im Bereich von 0 bis -150 km^-1, bevorzugt im Bereich von -25 bis -75 km^-1 festgelegt wird, und/oder
   2. (ii) bei Raumtemperatur im Bereich von <-200 km^-1, vorzugsweise -200 bis -400 km^-1, weiter bevorzugt im Bereich von -300 bis -350 km^-1 festgelegt wird;
   wobei bei Verwendung oder Einstellung anderer Schichtdicken (d_Saphir/d_GaN) der Krümmungswert in Abhängigkeit der jeweiligen Schichtdicken analog der Stoney-Gleichung im folgenden Bereich liegt: $${\mathrm{K}}_{\mathrm{T}\left(\mathrm{dGaN};\mathrm{dSaphir}\right)}={\mathrm{K}}_{\mathrm{T}\left(7\mu \mathrm{m};430\mu \mathrm{m}\right)}\times {\left(430\mu \mathrm{m}/{\mathrm{<figure-callout\; id="2"\; label="d\; Saphir"\; filenames="imgf0001.png,imgf0004.png"\; state="\{\{state\}\}">d</figure-callout>}}_{\mathrm{Saphir}}\right)}^2\times \left({\mathrm{d}}_{\mathrm{GaN}}/7\mu \mathrm{m}\right).$$
   
6. 6. Verfahren gemäß einem der vorangehenden Punkte, dadurch gekennzeichnet, dass der III-N-Einkristall des Templats bei Raumtemperatur einen Krümmungsradius im Bereich von -2 bis -6 m aufweist.
7. 7. Verfahren gemäß einem der vorangehenden Punkte, dadurch gekennzeichnet, dass im kristallinen III-N-Material eine kompressive Verspannung erzeugt wird.
   Die kompressive Verspannung wird primär dadurch erzeugt, dass die Zwischenschicht des Maskenmaterials ohne Abstand bzw. bei einem gezielt festgelegten Abstand vom Saphir-Substrat bzw. der Nukleationsschicht abgeschieden wird.
8. 8. Verfahren gemäß einem der vorangehenden Punkte, dadurch gekennzeichnet, dass der III-N-Einkristall des Templats bei Raumtemperatur eine kompressive Spannung von σ_xx<-0,70 GPa aufweist.
9. 9. Verfahren gemäß einem der vorangehenden Punkte, dadurch gekennzeichnet, dass die Zwischenschicht des Maskenmaterials auf einer III-N-Nukleationsschicht auf dem Fremdsubstrat abgeschieden wird und anschließend das Wachstum des III-N-Kristalls durchgeführt wird. Bei dieser Ausführungsform ist es bevorzugt, dass die Zwischenschicht des Maskenmaterials direkt und unmittelbar auf der III-N-Nukleationsschicht des Fremdsubstrats abgeschieden wird, noch bevor die Koaleszenz beendet ist und danach das eigentliche Wachstum des III-N-Einkristalls des Templats einsetzt.
10. 10. Verfahren gemäß einem der vorangehenden Punkte, dadurch gekennzeichnet, dass das Maskenmaterial bei der Herstellung des Templats auf dem Fremdsubstrat oder innerhalb der III-N-Schicht des Templats in situ in demselben Reaktor abgeschieden wird und/oder unmittelbar nach Abscheidung des Maskenmaterials mit dem III-N-Wachstumsprozess fortgesetzt wird.
11. 11. Verfahren gemäß einem der vorangehenden Punkte, dadurch gekennzeichnet, dass das Maskenmaterial im Templat in einer Ebene gleichmäßig verteilt ist, bevorzugt aber diskontinuierlich abgeschieden ist.
    Obgleich gemäß dieser möglichen Ausführungsformen das Maskenmaterial im Templat im Wesentlichen in einer Ebene vorliegt, kann die Form der Abscheidung unterschiedlich sein. Die Schicht des Maskenmaterials kann eine geschlossene Schicht bilden, alternativ und bevorzugt weist sie jedoch Unterbrechungen auf und ist diskontinuierlich in einer Schicht verteilt; sie kann insbesondere in Form von Netzstrukturen und/oder in Form von Nanoplättchen oder -inseln des Maskenmaterials vorliegen (Nano-Maske mit Maskenmaterial), wobei aus mikroskopischen oder nanodimensionierten Lücken in der diskontinuierlichen Maskenschicht heraus das nachfolgende Wachstum der III-N-Schicht nachfolgen kann. Auch die Dicke der Schicht des Maskenmaterials ist variabel. Den verschiedenen möglichen Abscheidungsformen ist eine jeweils günstige Beeinflussung von (Ver-)Spannung im gebildeten III-N-Kristall und/oder vom Krümmungsverhalten bzw. -zustand des Templats bei Wachstumstemperatur und/oder bei Raumtemperatur gemeinsam. Gewünschte Formen sind durch passende Parameter geeignet einstellbar, zum Beispiel durch Flussraten der entsprechenden Ausgangsmaterialien, durch Reaktordruck, durch Abscheidungstemperatur, oder durch Dauer der Abscheidung des Maskenmaterials.
12. 12. Verfahren gemäß einem der vorangehenden Punkte, dadurch gekennzeichnet, dass keine zweite SiN_x-Maske im Abstand von 1,5µm abgeschieden wird, oder dass überhaupt keine zweite SiN_x-Maske abgeschieden wird.
13. 13. Verfahren gemäß einem der vorangehenden Punkte, dadurch gekennzeichnet, dass im Templat nur eine einzige Schicht des Maskenmaterials abgeschieden wird.
14. 14. Verfahren gemäß einem der vorangehenden Punkte, dadurch gekennzeichnet, dass das Maskenmaterial ein Material ist, auf dem eine III-N-Abscheidung gehemmt oder verhindert ist.
15. 15. Verfahren gemäß dem vorangehenden Punkt, wobei das Maskenmaterial ausgewählt ist aus der Gruppe, die aus Si_xN_y (worin x und y jeweils unabhängig voneinander positive Zahlen bedeuten, die zu stöchiometrischen oder unstöchiometrischen SiN-Verbindungen führen; insbesondere Si₃N₄), TiN, Al_XO_Y (worin x und y jeweils unabhängig voneinander positive Zahlen bedeuten, die zu stöchiometrischen oder unstöchiometrischen AlO-Verbindungen führen; insbesondere Al₂O₃), Si_XO_Y (worin x und y jeweils unabhängig voneinander positive Zahlen bedeuten, die zu stöchiometrischen oder unstöchiometrischen SiO-Verbindungen führen; insbesondere SiO₂), WSi, und WSiN besteht. Beim Abscheiden des Maskenmaterials wird vorzugsweise das Maskenmaterial direkt im Reaktor in situ aus entsprechenden reaktiven Spezies der jeweiligen Elemente aus der Gasphase abgeschieden, und vorzugsweise wird direkt danach die Abscheidung des eigentlichen III-N-Kristalls des Templats gestartet bzw. fortgesetzt.
16. 16. Verfahren gemäß einem der vorangehenden Punkte, dadurch gekennzeichnet, dass das Fremdsubstrat aus Saphir besteht.
17. 17. Verfahren gemäß einem der vorangehenden Punkte, dadurch gekennzeichnet, dass die Krümmung des III-N-Kristalls des Templats in mindestens einer Wachstumsphase durch Variieren der Wachstumstemperatur zusätzlich verändert wird.
18. 18. Verfahren gemäß einem der vorangehenden Punkte, dadurch gekennzeichnet, dass in mindestens einer Abscheidungsphase des III-N-Kristalls des Templats das Wachstum bei einer gegenüber einer vorherigen III-N-Abscheidung abgesenkten Wachstumstemperatur erfolgt.
19. 19. Verfahren gemäß Punkt 18, dadurch gekennzeichnet, dass die Temperaturabsenkung mindestens 10°C, vorzugsweise mindestens 20 °C beträgt, bevorzugt im Bereich von 20-50 °C, weiter bevorzugt im Bereich von 25-40 °C und besonders bevorzugt bei 30°C liegt.
20. 20. Verfahren gemäß einem der vorangehenden Punkte, dadurch gekennzeichnet, dass das bereitgestellte Substrat eine polierte Oberfläche aufweist.
21. 21. Verfahren gemäß einem der vorangehenden Punkte, dadurch gekennzeichnet, dass das bereitgestellte Substrat eine durch Lithographie oder nasschemisches Ätzen oder trockenchemisches Ätzen (z.B. ICP) strukturierte Oberfläche aufweist.
22. 22. Verfahren gemäß einem der vorangehenden Punkte, dadurch gekennzeichnet, dass auf dem Templat oder auf dem darauf epitaxial aufgewachsenen III-N-Kristall mindestens eine und gegebenenfalls weitere GaN-, AlN-, AlGaN-, InN-, InGaN-, AlInN- oder AlInGaN-Schicht(en) zur Herstellung entsprechend weiterer III-N-Schichten oder III-N-Kristalle aufgebracht wird (werden).
23. 23. Verfahren gemäß einem der vorangehenden Punkte, dadurch gekennzeichnet, dass die III-N-Kristallschicht des Templats sowie der darauf epitaxial aufgewachsene III-N-Kristall aus demselben III-N Material bestehen.
24. 24. Verfahren gemäß einem der vorangehenden Punkte, dadurch gekennzeichnet, dass die III-N-Kristallschicht auf dem Fremdsubstrat sowie der darauf epitaxial aufgewachsene III-N-Kristall jeweils ein binäres System bilden.
25. 25. Verfahren gemäß einem der vorangehenden Punkte, wobei nach Abscheiden der Zwischenschicht des Maskenmaterials in situ zusätzliches Kristallwachstum zum Bilden von III-N-Kristall mit einer Gesamtdicke im Bereich von 0,1-10 µm erfolgt, vorzugsweise mit einer Dicke im Bereich von 3 bis 10 µm, wodurch ein Templat erhalten wird, wobei die Gesamtdicke der III-N-Schicht des Templats einschließlich der Zwischenschicht des Maskenmaterials gerechnet wird.
26. 26. Verfahren gemäß einem der vorangehenden Punkte, dadurch gekennzeichnet, dass MOVPE als Aufwachsmethode verwendet wird.
27. 27. Verfahren gemäß einem der vorangehenden Punkte, dadurch gekennzeichnet, dass auf dem Templat III-N-Einkristalle gewachsen werden mit Schichtdicken von mindestens 1 mm, bevorzugt von mindestens 5 mm, mehr bevorzugt von mindestens 7 mm und am meisten bevorzugt von mindestens 1 cm.
28. 28. Verfahren gemäß einem der vorangehenden Punkte, dadurch gekennzeichnet, dass das Kristallwachstum mindestens im Schritt nach Abschluss der Templatbildung, gegebenenfalls von Anfang an und in allen Kristallwachstumsschritten, mittels HVPE durchgeführt wird.
29. 29. Verfahren zur Herstellung von III-N-Einkristall gemäß einem der vorangehenden Punkte, dadurch gekennzeichnet, dass nach Abschluss des Kristallwachstums der gewachsene III-N-Einkristall und das Saphir umfassende Fremdsubstrat durch Selbstablösung voneinander getrennt werden, vorzugsweise beim Abkühlen von einer Kristallwachstumstemperatur.
30. 30. Verfahren zur Herstellung von III-N-Einkristall gemäß einem der vorangehenden Punkte, dadurch gekennzeichnet, dass nach Abschluss des Kristallwachstums der gewachsene III-N-Einkristall und das Saphir umfassende Fremdsubstrat durch Abschleifen, Absägen oder einen lift-off-Prozess voneinander getrennt werden.
31. 31. Verfahren zur Herstellung von III-N-Kristallwafern, wobei III mindestens ein Element der dritten Hauptgruppe des Periodensystems ausgesucht aus der Gruppe von Al, Ga und In bedeutet, wobei das Verfahren die folgenden Schritte umfasst:
    1. a) Durchführung eines Verfahrens gemäß einem der Punkte 3 bis 30 zum Bilden eines III-N-Massivkristalls, und
    2. b) Vereinzeln des Massivkristalls zum Bilden von Wafern.
32. 32. Templat mit einem Saphir umfassenden Substrat und mindestens einer III-N-Kristallschicht, wobei III mindestens ein Element der dritten Hauptgruppe des Periodensystems, ausgewählt aus der Gruppe von Al, Ga und In, bedeutet, wobei im Bereich über dem Fremdsubstrat oder in der III-N-Kristallschicht des Templats ein Maskenmaterial als Zwischenschicht vorgesehen ist, wobei in der III-N-Kristallschicht des Templats ein Wert ε_xx bei Raumtemperatur von ε_xx< 0 eingestellt ist.
33. 33. Templat mit einem Saphir umfassenden Substrat und mindestens einer III-N-Kristallschicht, wobei III mindestens ein Element der dritten Hauptgruppe des Periodensystems, ausgewählt aus der Gruppe von Al, Ga und In, bedeutet, wobei im Bereich über dem Fremdsubstrat oder in der III-N-Kristallschicht des Templats ein Maskenmaterial als Zwischenschicht vorgesehen ist, wobei in der III-N-Kristallschicht des Templats ein Wert ε_xx bei Wachstumstemperatur von ε_xx≤0 eingestellt ist, wobei ε_xx mit Hilfe einer Röntgenmessung der absoluten Gitterkonstante bestimmt ist, und wobei ein Abstand der Zwischenschicht des Maskenmaterials gegenüber dem Substrat bzw. der gegebenenfalls darauf gebildeten III-N-Nukleationsschicht maximal 50 nm beträgt.
34. 34. Templat gemäß Punkt 32 oder 33, wobei in der III-N-Kristallschicht des Templats der Wert ε_xx bei Raumtemperatur im Bereich 0 > ε_xx ≥ -0,003 und insbesondere im Bereich -0,0015> ε_xx ≥ -0,0025 und insbesondere im Bereich -0,0020 ≥ ε_xx ≥ -0,0025 eingestellt ist.
35. 35. Templat gemäß einem der Punkte 32 bis 34, wobei in der III-N-Kristallschicht des Templats der Wert ε_xx bei Wachstumstemperatur im Bereich von 0 > ε_xx > -0,0006, bevorzugt im Bereich von -0,0003 > ε_xx > -0,0006 liegt.
36. 36. Templat gemäß einem der Punkte 32 bis 35 in Form eines Templats mit einer Schichtdicke des III-N-Einkristalls im Bereich von 0,1-10 µm, bevorzugt von 2-5 µm, gerechnet inklusive Zwischenschicht des Maskenmaterials.
37. 37. Templat gemäß einem der Punkte 32 bis 36, dadurch gekennzeichnet, dass der III-N-Einkristall bei Raumtemperatur eine kompressive Spannung von σ_xx<-0,70 GPa aufweist.
38. 38. Templat gemäß einem der Punkte 32 bis 37, dadurch gekennzeichnet, dass wenn für das Templat als Fremdsubstrat Saphir einer Dicke (d_Saphir) von ungefähr 430µm (d.h. ±20µm) und als III-N-Kristallschicht des GaN einer Dicke (d_GaN) von ungefähr 7µm (d.h. ±0,5µm) verwendet oder eingestellt wird,
    beim III-N-Kristall eine Krümmung des Templats (K_T)
    1. (i) bei Wachstumstemperatur im Bereich von 0 bis -150 km^-1, bevorzugt im Bereich von -25 bis -75 km^-1 festgelegt ist; und/oder
    2. (ii) bei Raumtemperatur im Bereich von -200 bis -400 km^-1, bevorzugt im Bereich von -300 bis -400 km^-1, weiter bevorzugt im Bereich von -300 bis -350 km^-1 festgelegt ist,
    wobei bei Verwendung oder Einstellung anderer Schichtdicken (d_Saphir/d_GaN) der Krümmungswert in Abhängigkeit der jeweiligen Schichtdicken analog der Stoney-Gleichung in folgenden Bereich liegt: $${\mathrm{K}}_{\mathrm{T}\left(\mathrm{dGaN};\mathrm{dSaphir}\right)}={\mathrm{K}}_{\mathrm{T}\left(7\mu \mathrm{m};430\mu \mathrm{m}\right)}\times {\left(430\mu \mathrm{m}/{\mathrm{<figure-callout\; id="2"\; label="d\; Saphir"\; filenames="imgf0001.png,imgf0004.png"\; state="\{\{state\}\}">d</figure-callout>}}_{\mathrm{Saphir}}\right)}^2\times \left({\mathrm{d}}_{\mathrm{GaN}}/7\mu \mathrm{m}\right).$$
    
39. 39. Templat gemäß einem der Punkte 32 bis 38, dadurch gekennzeichnet, dass III = Ga bedeutet und der Kristall in Wachstumsrichtung eine Gitterkonstante im Bereich von 0,31829 nm < a < 0,318926 nm aufweist.
40. 40. Templat gemäß einem der Punkte 32 bis 39, dadurch gekennzeichnet, dass das Saphir umfassende Substrat entfernt ist.
41. 41. Templat gemäß einem der Punkte 32 bis 40, hergestellt nach oder verwendet in einem der Verfahren gemäß den Punkte 1 bis 31.
42. 42. Verwendung von nach Punkt 31 hergestellten III-N-Wafern, oder Verwendung eines Templats gemäß einem der Punkte 32 bis 41 zur Herstellung von dickeren III-N-Schichten oder III-N-Kristallboules bzw. -Massivkristallen, die optional danach in einzelne III-N-Wafer vereinzelt werden.
43. 43. Verwendung von nach Punkt 31 hergestellten III-N-Wafern, oder Verwendung eines Templats gemäß einem der Punkte 32 bis 41, jeweils zur Herstellung von Halbleiterelementen, elektronischen oder optoelektronischen Bauelementen.
44. 44. Verwendung gemäß Punkt 43 zur Herstellung von Leistungsbauelementen, Hochfrequenzbauelementen, lichtemittierenden Dioden und Lasern.
45. 45. Verwendung eines Maskenmaterials als Zwischenschicht in einem Templat, welches ein Saphir umfassendes Substrat und eine III-N-Kristallschicht aufweist, wobei III mindestens ein Element der dritten Hauptgruppe des Periodensystems, ausgewählt aus der Gruppe von Al, Ga und In, bedeutet, zum Steuern eines Krümmungswerts und/oder einer Verspannung des Templats, um nach Einstellung eines bestimmten Krümmungswerts und/oder einer bestimmten Verspannung mindestens eine weitere III-N-Kristallschicht auf dem Substrat aufzubringen, wobei ein Abstand der Zwischenschicht des Maskenmaterials gegenüber dem Substrat bzw. der gegebenenfalls darauf gebildeten III-N-Nukleationsschicht vorliegt und maximal 50 nm beträgt.
46. 46. Verwendung gemäß Punkt 45, wobei der bestimmte Krümmungswert und/oder die bestimmte Verspannung eine Rissbildung in einem anschließenden weiteren Wachstum einer zusätzlichen III-N-Schicht vermeidet.

The following is a summary of items describing articles, developments, and particular features of the present disclosure:

1. A process for producing a template comprising a substrate and at least one III-N crystal layer, wherein III means at least one element of the third main group of the periodic table selected from Al, Ga and In, said method comprising the steps of providing a substrate and
   Growth of a crystalline III-N material on the substrate
   wherein a mask material as an intermediate layer on the substrate, which optionally has a III-N nucleation layer, or in the crystalline III-N material at a distance from the substrate or the optionally provided III-N nucleation layer is deposited and then the growth of a takes place or continues, wherein the distance of the intermediate layer of the mask material from the substrate or the III-N nucleation layer optionally formed thereon is a maximum of 50 nm,
   and wherein if, during crystal growth, the curvature of the growth surface of the III-N crystal is denoted by K _a at a first, relatively earlier time and K _e at a second, relatively later time, for a curvature difference (K _a -K _e ) ≥ 0 is taken care of.
   The range K _a -K _e > 0 is preferred.
   The substrate is formed as a foreign substrate, ie, a material which is different from the III-N material of the template, in particular the foreign substrate comprises sapphire or consists of sapphire.
   The mask material is suitably defined as a material other than substrate material and III-N on which III-N growth is inhibited, disrupted or prevented. Examples of the mask material are described below.
   The terms "relatively early" and "relatively late" means a first or second time during crystal growth, which may be the beginning and end of the total crystal growth of the III-N crystal layer, but also only a certain phase of the total crystal growth of III -N crystal layer can define and it does not matter in the last case, as the Curvature behavior before the first or after the second time is. For example, but not limited to, the relatively early first time is given by the time of application of the intermediate layer of mask material, and for example, the relatively late second time given by the end of the template fabrication stage is again, but not limited thereto be. Common to the possible variants of the respective times is in each case a favorable influence on (supply) voltage in the III-N crystal formed and / or on the bending behavior or state of the template at growth temperature and / or at room temperature, in each case in comparison to failure to observe mentioned relationship K _a -K _e . The term "interlayer" is to be understood in a broad sense, usually as a material layer comprising mask material, optionally in addition to mask material still further material such as the III-N material comprises or has material-free gaps. The thickness of the "intermediate layer" is variable, but is usually thin to very thin, suitably in the nanometer range (eg up to a maximum of 50 nm, preferably below 5 nm) or in the subnanometer range (eg to less than 1 nm, in particular to under a monolayer, ie 0.2 to 0.3 nm or less).
   Depositing the mask material of the intermediate layer "on the substrate" means directly adjacent to a surface of the sapphire or the optional III-N nucleation layer over the sapphire (not according to the invention), and "at a distance from the substrate" means the distance of the position of the sapphire Mask material interlayer from this surface.
2. 2. The method according to item 1, characterized in that the curvature difference (K _a -K _e ) is at least 5 km ^-1 , preferably at least 10 km ^-1 , more preferably at least 20 km ^-1 and in particular at least 50 km ^-1 .
3. 3. Method according to item 1 or 2, wherein the template is further used for applying one or more further III-N crystal layer (s), optionally for producing a III-N solid crystal.
   Because the prepared template is favorably influenced according to the invention by considering the curvature difference K _a -K _e , the further curvature preservation of the growth surface of the III-N crystal during an optionally subsequent application or growth of further semiconductor material is not fixed.
4. 4. A process for the preparation of III-N single crystal, wherein III means at least one element of the third main group of the periodic table, selected from Al, Ga and In, the process comprising the following steps:
   • aa) providing a template comprising a sapphire-containing foreign substrate and a III-N crystal layer, wherein the template is not or substantially not curved in the region of a growth temperature or is negatively curved, wherein in the template provided in the Over the foreign substrate or in the III-N crystal layer of the template, a mask material is deposited as an intermediate layer so that a distance of the intermediate layer of the mask material to the substrate or the optionally formed thereon III-N nucleation layer is a maximum of 50 nm;
   • bb) performing an epitaxial crystal growth to form further III-N crystal on the template according to aa), optionally for producing III-N solid crystal,
   • cc) optionally separating III-N single crystal or III-N solid crystal and foreign substrate. According to the invention, it is preferred that the desired favorable non-curvature or (compressive or convex) negative curvature of the template when it is heated in the initial state, ie before the further growth according to step bb), by targeted positioning of an intermediate layer of the mask material in a defined and limited altitude on / above the foreign substrate. For this purpose and to express "intermediate layer" s. the above points 1 and 2.
   In addition, if this measure is not or not sufficient for the stated condition, additional parameters may be additionally considered and adjusted, for example by varying the growth temperature (reduction due to the choice of sapphire) during a limited phase of growth of the III-N layer of the template as a foreign substrate) and thus a supplementary and / or alternative contribution to the relationship K _a -K _e ≥ 0 was delivered.
   The term "growth temperature" refers to a temperature at which deposition, in particular epitaxial growth, of a desired III-N crystal is enabled.
5. 5. Method according to one of the preceding points, characterized in that if, for the template as a foreign substrate, sapphire of a thickness (d _sapphire ) of approximately 430μm (ie ± 20μm) and as a III-N crystal layer of GaN of a thickness (d _GaN ) of about 7 μm (ie ± 0.5 μm) is used or set,
   for the III-N crystal, a curvature of the template (K _T ) at the growth surface
   1. (i) is set at growth temperature in the range of 0 to -150 km ^-1 , preferably in the range of -25 to -75 km ^-1 , and / or
   2. (ii) is set at room temperature in the range of <-200 km ^-1 , preferably -200 to -400 km ^-1 , more preferably in the range of -300 to -350 km ^-1 ;
   wherein, when using or setting other layer thicknesses (d _sapphire / d _GaN ), the curvature value as a function of the respective layer thicknesses is in the following range analogous to the Stoney equation: $${\mathrm{K}}_{\mathrm{T}\left(\mathrm{dgan};\mathrm{dSaphir}\right)}={\mathrm{K}}_{\mathrm{T}\left(7\mu \mathrm{m};430\mu \mathrm{m}\right)}\times {\left(430\mu \mathrm{m}/{\mathrm{<figure-callout\; id="2"\; label="d\; sapphire"\; filenames="imgf0001.png,imgf0004.png"\; state="\{\{state\}\}">d\; </figure-callout>}}_{\mathrm{sapphire}}\right)}^2\times \left({\mathrm{d}}_{\mathrm{GaN}}/7\mu \mathrm{m}\right),$$
   
6. 6. The method according to any one of the preceding points, characterized in that the III-N single crystal of the template at room temperature has a radius of curvature in the range of -2 to -6 m.
7. 7. The method according to any one of the preceding points, characterized in that in the crystalline III-N material, a compressive strain is generated.
   The compressive stress is generated primarily by the fact that the intermediate layer of the mask material is deposited without distance or at a specifically defined distance from the sapphire substrate or the nucleation layer.
8. 8. The method according to any one of the preceding points, characterized in that the III-N single crystal of the template at room temperature has a compressive stress of σ _xx <-0.70 GPa.
9. 9. The method according to one of the preceding points, characterized in that the intermediate layer of the mask material is deposited on a III-N nucleation layer on the foreign substrate and then the growth of the III-N crystal is carried out. In this embodiment, it is preferable that the intermediate layer of the mask material is deposited directly and immediately on the III-N nucleation layer of the foreign substrate even before the coalescence is completed and thereafter the actual growth of the III-N single crystal of the template.
10. 10. The method according to one of the preceding points, characterized in that the mask material in the preparation of the template on the foreign substrate or within the III-N layer of the template is deposited in situ in the same reactor and / or immediately after deposition of the mask material with the III-N growth process continues.
11. 11. The method according to any one of the preceding points, characterized in that the mask material is uniformly distributed in the template in a plane, but preferably is discontinuous deposited.
    Although according to these possible embodiments, the mask material in the template is substantially in one plane, the shape of the deposit may be different. The layer of masking material may form a closed layer, but alternatively and preferably it has discontinuities and is discontinuously distributed in a layer; it can be present in particular in the form of network structures and / or in the form of nanoplates or islands of the mask material (nano-mask with mask material), wherein the subsequent growth of the III-N layer can follow from microscopic or nanodimensioned gaps in the discontinuous mask layer , The thickness of the layer of the mask material is variable. The various possible forms of deposition are in each case a favorable influence on (supply) voltage in the III-N crystal formed and / or on the curvature behavior or state of the template at growth temperature and / or at room temperature. Desired shapes are suitably adjustable by suitable parameters, for example by flow rates of the corresponding ones Starting materials, by reactor pressure, by deposition temperature, or by the duration of deposition of the mask material.
12. 12. The method according to one of the preceding points, characterized in that no second SiN _x mask is deposited at a distance of 1.5 .mu.m, or that no second SiN _x mask is deposited at all.
13. 13. Method according to one of the preceding points, characterized in that only a single layer of the mask material is deposited in the template.
14. 14. The method according to one of the preceding points, characterized in that the mask material is a material on which a III-N deposition is inhibited or prevented.
15. 15. A method according to the preceding item, wherein the masking material is selected from the group consisting of Si _x N _y (wherein x and y are each independently positive numbers which result in stoichiometric or unstoichiometric SiN compounds, in particular Si ₃ N ₄ ), TiN, Al _x O _y (wherein x and y are each independently positive numbers which result in stoichiometric or unstoichiometric Al ₂ O ₃ compounds, particularly Al ₂ O ₃ ), Si _x O _y (where x and y are each independently positive Mean numbers which lead to stoichiometric or unstoichiometric SiO ₂ compounds, in particular SiO ₂ ), WSi, and WSiN. When depositing the mask material, the mask material is preferably deposited directly in the reactor in situ from corresponding reactive species of the respective elements from the gas phase, and preferably immediately after the deposition of the actual III-N crystal of the template is started or continued.
16. 16. The method according to one of the preceding points, characterized in that the foreign substrate consists of sapphire.
17. 17. The method according to any one of the preceding points, characterized in that the curvature of the III-N crystal of the template is additionally changed in at least one growth phase by varying the growth temperature.
18. 18. The method according to any one of the preceding points, characterized in that in at least one deposition phase of the III-N crystal of the template, the growth takes place at a reduced compared to a previous III-N deposition growth temperature.
19. 19. The method according to item 18, characterized in that the temperature reduction is at least 10 ° C, preferably at least 20 ° C, preferably in the range of 20-50 ° C, more preferably in the range of 25-40 ° C and particularly preferably at 30 ° C is.
20. 20. Method according to one of the preceding points, characterized in that the substrate provided has a polished surface.
21. 21. Method according to one of the preceding points, characterized in that the provided substrate has a surface structured by lithography or wet-chemical etching or dry-chemical etching (eg ICP).
22. 22. Method according to one of the preceding points, characterized in that on the template or on the III-N crystal epitaxially grown thereon at least one and optionally further GaN, AlN, AlGaN, InN, InGaN, AlInN or AlInGaN layer (s) is applied to produce correspondingly further III-N layers or III-N crystals.
23. 23. Method according to one of the preceding points, characterized in that the III-N crystal layer of the template and the epitaxially grown III-N crystal consist of the same III-N material.
24. 24. The method according to any one of the preceding points, characterized in that the III-N crystal layer on the foreign substrate and the epitaxially grown there on III-N crystal each form a binary system.
25. 25. Method according to one of the preceding points, wherein, after deposition of the intermediate layer of the mask material in situ, additional crystal growth takes place to form III-N crystal with a total thickness in the range of 0.1-10 μm, preferably with a thickness in the range of 3 to 10 .mu.m, whereby a template is obtained, whereby the total thickness of the III-N layer of the template including the intermediate layer of the mask material is calculated.
26. 26. Method according to one of the preceding points, characterized in that MOVPE is used as a growth method.
27. 27. Method according to one of the preceding points, characterized in that III-N monocrystals are grown on the template with layer thicknesses of at least 1 mm, preferably of at least 5 mm, more preferably of at least 7 mm and most preferably of at least 1 cm ,
28. 28. The method according to one of the preceding points, characterized in that the crystal growth is carried out at least in the step after completion of the template formation, optionally from the beginning and in all crystal growth steps, by means of HVPE.
29. 29. A method for producing III-N single crystal according to any one of the preceding points, characterized in that after completion of the crystal growth, the grown III-N single crystal and the sapphire-containing foreign substrate are separated from each other by self-peeling, preferably, upon cooling from a crystal growth temperature.
30. 30. A method for producing III-N single crystal according to any one of the preceding points, characterized in that after completion of the crystal growth of the grown III-N single crystal and the sapphire-comprising foreign substrate are separated by abrasion, sawing or a lift-off process.
31. 31. A process for the preparation of III-N crystal wafers, wherein III means at least one element of the third main group of the periodic table selected from the group of Al, Ga and In, the process comprising the following steps:
    1. a) performing a method according to any one of items 3 to 30 to form a III-N solid crystal, and
    2. b) singulating the solid crystal to form wafers.
32. 32. A template comprising a sapphire substrate and at least one III-N crystal layer, wherein III at least one element of the third main group of the periodic table, selected from the group of Al, Ga and In, means in the area above the foreign substrate or in the III-N crystal layer of the template, a mask material is provided as an intermediate layer, wherein in the III-N crystal layer of the template a value ε _xx at room temperature of ε _xx <0 is set.
33. 33. A template comprising a sapphire-comprising substrate and at least one III-N crystal layer, III being at least one element of the third main group of the periodic table, selected from the group of Al, Ga and In, where in the region above the foreign substrate or in the III-N crystal layer of the template, a mask material is provided as an intermediate layer, wherein in the III-N crystal layer of the template, a value ε _{xx is set} at growth temperature of ε _xx ≤0, where ε _{xx is determined} by means of an X-ray measurement of the absolute lattice constant , and wherein a distance of the intermediate layer of the mask material relative to the substrate or the optionally formed thereon III-N nucleation layer is a maximum of 50 nm.
34. 34. template according to item 32 or 33, wherein in the III-N crystal layer of the template the value ε _xx at room temperature in the range 0> ε _xx ≥ -0.003 and in particular in the range -0.0015> ε _xx ≥ -0.0025 and in particular in the range -0.0020 ≥ ε _xx ≥ -0.0025.
35. 35. Template according to one of the items 32 to 34, wherein in the III-N crystal layer of the template the value ε _xx at a growth temperature in the range of 0> ε _xx > -0.0006, preferably in the range of -0.0003> ε _xx > -0.0006.
36. 36. Template according to one of the points 32 to 35 in the form of a template with a layer thickness of the III-N single crystal in the range of 0.1-10 μm, preferably 2-5 μm, including the intermediate layer of the mask material.
37. 37. Template according to one of the points 32 to 36, characterized in that the III-N single crystal at room temperature has a compressive stress of σ _xx <-0.70 GPa.
38. 38. Template according to one of the points 32 to 37, characterized in that when for the template as a foreign substrate sapphire of a thickness (d _sapphire ) of about 430μm (ie ± 20μm) and as a III-N crystal layer of GaN a thickness (d _GaN ) of approximately 7μm (ie ± 0.5μm) is used or adjusted,
    for the III-N crystal, a curvature of the template (K _T )
    1. (i) is set at growth temperature in the range of 0 to 150 km ^-1 , preferably in the range of -25 to -75 km ^-1 ; and or
    2. (ii) is set at room temperature in the range of -200 to -400 km ^-1 , preferably in the range of -300 to -400 km ^-1 , more preferably in the range of -300 to -350 km ^-1 ,
    wherein, when using or adjusting other layer thicknesses (d _sapphire / d _GaN ), the curvature value as a function of the respective layer thicknesses is in the following range analogous to the Stoney equation: $${\mathrm{K}}_{\mathrm{T}\left(\mathrm{dgan};\mathrm{dSaphir}\right)}={\mathrm{K}}_{\mathrm{T}\left(7\mu \mathrm{m};430\mu \mathrm{m}\right)}\times {\left(430\mu \mathrm{m}/{\mathrm{<figure-callout\; id="2"\; label="d\; sapphire"\; filenames="imgf0001.png,imgf0004.png"\; state="\{\{state\}\}">d\; </figure-callout>}}_{\mathrm{sapphire}}\right)}^2\times \left({\mathrm{d}}_{\mathrm{GaN}}/7\mu \mathrm{m}\right),$$
    
39. 39. Template according to one of the points 32 to 38, characterized in that III = Ga means and the crystal in the growth direction has a lattice constant in the range of 0.31829 nm <a <0.318926 nm.
40. 40. Template according to one of the points 32 to 39, characterized in that the substrate comprising sapphire is removed.
41. 41. Template according to any one of items 32 to 40, prepared according to or used in one of the methods according to items 1 to 31.
42. 42. Use of III-N wafers prepared according to item 31, or use of a template according to any one of items 32 to 41 for the preparation of thicker III-N layers or III-N crystal boules, optionally thereafter into individual Separate III-N wafers.
43. 43. Use of III-N wafers prepared according to item 31, or use of a template according to any one of items 32 to 41, in each case for the production of semiconductor elements, electronic or optoelectronic components.
44. 44. Use according to item 43 for the manufacture of power devices, high frequency devices, light emitting diodes and lasers.
45. 45. Use of a masking material as an intermediate layer in a template comprising a sapphire substrate and a III-N crystal layer, wherein III means at least one element of the third main group of the periodic table selected from the group of Al, Ga and In, for Controlling a curvature value and / or a strain of the template to apply after setting a certain curvature value and / or a certain strain at least one further III-N crystal layer on the substrate, wherein a distance of the intermediate layer of the Mask material opposite to the substrate or the optionally formed thereon III-N nucleation layer is present and a maximum of 50 nm.
46. 46. Use according to item 45, wherein the determined curvature value and / or the particular strain avoids cracking in subsequent further growth of an additional III-N layer.

The temperatures stated in the application, unless stated otherwise, refer to the temperatures set corresponding to heaters, i. nominally set temperatures for respective steps (process temperature). The temperatures at the template / wafer are typically slightly lower, which may vary depending on the type of reactor; e.g. down to 75K. Thus, in the reactor type used in the examples, the temperatures at the template / wafer (measured with an in-situ measuring instrument EpiTT from Laytec, Berlin, Germany) are about 30-50K below the process temperature.

BRIEF DESCRIPTION OF THE FIGURES

Fig. 1A and 1B

schematically show steps of the growth process for forming III-N templates with sapphire substrate, and each with different embodiments according to the present invention;

Fig. 2

illustrates temporal temperature, reflection and curvature patterns in the exemplary growth of GaN on sapphire (distance 15 nm);

Fig. 3

illustrates temporal temperature, reflection and curvature curves with growth of GaN on sapphire (distance 300 nm);

Fig. 4

Figure 12 shows the change in the curvature of the growth surface according to another principle, optionally combining deposition of an intermediate layer with mask material with a change in III-N growth temperature during growth of the III-N layer of the template;

Figs. 5A and 5B

show the change of the curvature of the growth surface mainly depending on the provision and location / positioning of an intermediate layer with mask material according to various possible embodiments of the present invention,

Fig. 5C

shows the results regarding curvature of the growth surface when the according to Fig. 5A and 5B are subjected to further III-N (GaN) layer growth to produce thicker layers, and

Fig. 6

illustrates temporal temperature, reflection and curvature trajectories in conventional growth of GaN on sapphire.

Without limiting the present invention, the following detailed description of the figures, objects, further developments and special features is intended to illustrate the invention and to describe specific embodiments in more detail.

In the process for preparing III-N seed substrates, it has surprisingly been found that the template can be significantly influenced by suitable positioning of an intermediate layer of mask material with respect to the relevant parameter growth surface curvature on the template and / or appropriate strain in the template such that the subsequent growth of III-N single crystals with outstanding properties is made possible, and in particular the subsequent tendency to crack formation in growing on the template III-N single crystals is significantly reduced.

For the preparation of the template, a substrate is initially provided, which is selected from sapphire-containing or sapphire starting substrates and such starting substrates with structures formed thereon, for example, certain external ( ex situ ) formed mask structures. A further possibility of providing a suitable starting substrate may include the formation of intermediate layers or intermediate structures for the purpose of assisting the subsequent detachment from the starting substrate, and / or the formation of a so-called GaN nanorase, in which a substrate having a GaN substrate formed thereon is used. Complianz layer starting with nano-column structure, such as in WO2006035212A1 . WO2008096168A1 . WO2008087452A1 . EP2136390A2 and WO2007107757A2 described.
An optionally performed ex situ patterning such as the opening of windows and other mask structures thus belongs at best to the step of providing the starting substrate, but not to the actual step of introducing the mask intermediate layer, as described below in connection with the inventive method.

For the provision of a starting substrate, a foreign substrate with sapphire is used, preferably it is sapphire. More preferably, a c-orientation sapphire substrate is used with a tilt of (1-100) or (11-20) around 0.1-0.5 ° and single-sided epi-ready polish and polished and / or preferably lapped back. A further embodiment provides that the starting substrate has a surface structured by lithography or by wet-chemical or dry chemical etching (eg ICP etching).

Exemplary, non-limiting, but each varied embodiments will now be described with reference to the schematic Fig. 1A and 1B described. It should be noted here that the thickness of a substrate (BZ 100A or 100B) is substantially larger than the thicknesses of III-N material and layers formed thereon, and further that a major part of the grown III-N Layer of the template (b.105A and 105B, respectively) is substantially larger than a thickness of III-N material (b.103A and 103B respectively) below the intermediate layer with mask material (b.p. 102A and 102B, respectively), caused by respective breaks is indicated on the respective left edge of the layers 100A / 100B and 105A / 105B.
In the Figures 1A and 1B the provision of the respective substrates 100A and 100B is first shown in the same step (1). The respective substrates may optionally be pretreated as described above, in particular they may each be subjected to a desorption step and a nucleation step. In such an optional desorption step, for example, hydrocarbon radicals, but also other volatile impurities, can be removed from the starting substrate or structured or otherwise pretreated substrate. During the desorption step, the starting substrate is heated in the process to an elevated temperature, preferably to a temperature of 1100 to 1300 ° C, more preferably to a temperature of 1150 to 1250 ° C, eg, about 1200 ° C. Typically, due to the temperature gradient within the substrate, the starting substrate is subject to warping (warping, curvature), usually with a concave curvature with respect to the surface on which subsequently the III-N material is deposited. The desorption step may also optionally be followed by nitriding with ammonia. Another optional step is that after desorption, the temperature is lowered, for example to a temperature between 400 and 600 ° C, preferably to a temperature between 450 and 550 ° C. During this cooling, the - typically concave - curvature decreases again, for example to the level as at the beginning of the heating to the desorption step.

Provision and pretreatment of a substrate in the method of making a template of the present invention may preferably further comprise a nucleation step of growing crystalline III-N material, especially minute III-N crystallites, onto the starting substrate. This step is schematically in so far same step (2) of Fig. 1A and 1B shown. The crystalline III-N material 101A or 101B, especially the III-N crystallites serve as crystallization nuclei in the subsequent further III-N crystal growth. III-N crystallites have sizes of z. B. 1 to 40 nm with irregular shapes, are usually disordered on the starting substrate and form suitably first a non-contiguous nucleation layer. This nucleation step typically occurs at temperatures of 400 to 600 ° C, preferably 450 to 550 ° C, and more preferably 500 to 540 ° C in the case of low temperature GaN nucleation.
AlN nucleation typically occurs at temperatures of 850 to 1050 ° C, preferably 900 to 1000 ° C, and more preferably 950 to 960 ° C.
In the case of the low-temperature nucleation step, if appropriate also during the subsequent heating to growth temperature, an optional recrystallization can take place.

After providing a substrate, optionally with the optional measures described above, the further steps of the respective embodiments according to the invention may vary as far as the time and position of the layer of the mask material and the consequences resulting therefrom, as separated in each case Fig. 1A and Fig. 1B illustrated.
At the in Fig. 1A In the embodiment shown, an intermediate layer of mask material 102A is already applied directly to the nucleation layer 101A, even before coalescence of the crystallites occurs. In a further (not specifically shown here) modification, this deposition of the intermediate layer does not take place directly on the nucleation layer, but only after a very short phase of III-N growth, but still very close in the nm range at the nucleation layer, for example in a range of up to 30nm distance. In this distance range selected very close to the nucleation layer, the subsequent steps proceed practically analogously to those in FIG Fig. 1A shown form. At the in Fig. 1B In the embodiment shown, nucleation layer 101B is first of all subjected to a III-N growth for a specific, generally still relatively short time, for example until it has a small thickness of 30 nm or above and suitably up to about 300 nm, preferably to about 100 nm, and according to the invention to about 50 nm of the crystalline III-N layer 103B has formed, and only then an intermediate layer of mask material 102B is applied at the appropriate distance from the nucleation layer of the substrate.

The deposition of the designated intermediate layer 102A or 102B is conveniently and advantageously done in situ in the same reactor using a process compatible with the III-N layer growth technique. For this purpose, suitable starting materials or reactive secondary products or species of the mask material in the reactor at a suitable temperature and other parameters which are suitable for the deposition of mask material, reacted with each other. The simplest way is to deposit nitride mask material, such as silicon nitride, because its deposition is well compatible with III-N deposition techniques. Often, for this Deposition same or similar, or at least compatible conditions are selected in terms of reactor pressure and temperature as in the III-N deposition and otherwise adapted only suitable gas compositions and gas flow rates, so this process modification is easy to handle. Thus, for example, a silane gas and ammonia are flowed into the reactor and at a suitable pressure and suitable temperature of, for example, 800 ° C. to 1200 ° C., preferably about 1050 to 1150 ° C. with one another for the reaction and in the form of Si ₃ N ₄ and optionally further stoichiometric or over or substoichiometric Si _x N _y compositions deposited on the prepared substrate (100A, 101A). The step of depositing mask materials other than SiN, such as TiN, Al ₂ O ₃ , SiO ₂ , WSi, and WSiN, can be easily and appropriately adjusted.

On the nucleation layer (cf. Fig. 1A ; 101A) or alternatively on the currently growing, but still very close to the nucleation layer III-N layer (see. Fig. 1B ; 101B) thus forms a mask layer (102A and 102B, respectively). The mask layer may have different shapes. It is usually evenly distributed on the surface and can form a closed layer, but alternatively it has rather microscopic / nanostructured voids; these possibilities are shown schematically in the drawing in the form of a dashed layer 102A and 102B, respectively.
The thickness of the "intermediate layer" 102A or 102B, which respectively comprises mask material, is very small, which can be adjusted by appropriate gas flow rates and short process times; it is suitably in the nanometer or sub-nanometer range, for example below 5 nm, more preferably below 1 nm, in particular below one monolayer (ie 0.2 to 0.3 nm or less).
The distance of the intermediate layer 102A or 102B, from the substrate is low, it is in the range up to a maximum of 50 nm.

After deposition of the intermediate layer with mask material, the (continued) growth of a III-N layer 104A, 104B (step (4) in FIG Fig. 1A / 1B ) until the template is at the end of growth (step (5) in Fig. 1A / 1B ) has a III-N layer 105A, 105B of desired thickness in the range of 0.1-10 μm, preferably in the range of 3 to 10 μm (total thickness of the III-N layer of the template including the intermediate layer of the mask material and optionally nucleation). According to the invention, it is ensured that the characteristics of curvature (measured on the growth surface) and / or strain of the III-N layer of the template are favorably influenced and utilized for subsequent processes. So in contrast to Conventional procedure, in which typically forms a concave curvature of the growth surface, which then further increases in the course of further crystal growth, ie with increasing thickness of the III-N layer, according to the invention causes the curvature of the template during the subsequent further growth of a growing III-N layer 104A or 104B decreases, as in the respective steps (4) of Fig. 1A / 1B shown schematically. So in the special case of Fig. 1A Immediately following deposition of the intermediate layer of mask material 101A with coalescence of the III-N layer, this growing III-N layer curves atypically-negative-convexly, thereby establishing a desirable compressive strain in the template. In the special case of Fig. 1B While in step (3) there is initially a slight concave curvature with tensile strain in the III-N crystal 103B, in this case the curvature is at least significantly less increased than compared to a situation without deposition of the mask layer 102B at a suitable position / position, possibly even a decrease in the curvature is achieved and thus a curvature difference K _a -K _e ≥ 0 is observed.

If the desired curvature behavior is not achieved or not achieved solely by the position / position of the intermediate layer with mask material at a suitable distance from the surface of the foreign substrate or the nucleation layer, this behavior can be controlled by additionally and specifically setting other process parameters for the purpose of making a supplementary contribution to the relationship K _a -K _e ≥ 0, or that the template is substantially non-curved or negatively curved at growth temperature. A particularly suitable new process parameter for this purpose is an adaptation and possibly a variation of the III-N growth temperature. In the case of using sapphire as a foreign substrate which has a higher coefficient of thermal expansion than the III-N crystal to be grown, the growth / deposition occurs at a growth temperature lowered from previous growth. This temperature change is most effectively carried out during a limited, preferably relatively early, phase of growth of the III-N layer of the template, and growth is continued at this reduced temperature. Substantial curvature reduction with K _a -K _e > 0 is additionally achieved, for example, by the growth temperature being lowered by at least 10 ° C. in at least one growth phase of the III-N crystal of the template. The lowering of the growth temperature is preferably at least 20 ° C and more preferably in the range of 20-50 ° C and especially in the range of 25-40 ° C.

In the case of GaN, a common growth temperature is, for example, in the range of 900 ° C to 1200 ° C, preferably about 1020 to 1150 ° C, more preferably about 1100 ° C ± 20 ° C ,. For example, in the case of AlGaN having an Al content of 30% to 90%, a usual growth temperature is in the range of 1070-1,250 ° C, preferably 1,090-1,270 ° C, and more preferably 1,170 ° C. Temperatures for the deposition of other III-N materials are adjusted based on general knowledge.
If applicable and optionally desired, as described in the above-referenced specific embodiment, the system may first be brought to a correspondingly preselected (first) temperature, at which first temperature possibly only recrystallization takes place and this first temperature is then varied but only so far to a changed (second) temperature at which crystal growth, and preferably epitaxial crystal growth, can continue to take place in order to optionally additionally influence the curvature behavior. If optionally employed, this is preferably done at the onset or coalescence of the growing III-N crystallites or in the early phase of the growing III-N layer of the template. Due to the choice of sapphire as a foreign substrate, the growth temperature is lowered. When the (preferably epitaxial) crystal growth continues in the region of the correspondingly varied second growth temperature-ie below the respective first temperature-the curvature of the growth surface then decreases continuously or intermittently. As soon as a sufficient complementary decrease in curvature is achieved via this optional step of temperature variation, the temperature for the further growth of the III-N layer can be freely selected again, for example in the range of the usual growth temperatures mentioned above, such as for GaN and AlGaN.

The III component, starting from previous steps - such as in the formation of the initial III-N crystallites or the nucleation layer on the substrate as described above - can remain the same when changing to the epitaxial III-N epitaxial growth step, or alternatively it can be varied. For example, the nucleation layer (see 102A and 102B in FIG Fig. 1A / B ) may be formed of GaN or AlN, and independently, the epitaxial III-N layer of the template (see 104A-105A and 104B-105B in FIG Fig. 1A / B ) may be formed of GaN or AlGaN (preferably GaN). In a particular embodiment, the III components are not changed.

Again to the embodiments specifically described herein Fig. 1A and 1B In accordance with the invention, it is ensured that by suitable deposition of a single intermediate layer of the mask material 102A or 102B in the course of the further growth of the entire III-N layer 105A or 105B of the template in the micrometer range (usually up to 10 microns), the curvature continues to decrease, in the case of Fig. 1A with tendency to further negative curvature values, in the case of Fig. 1B on the other hand, because starting from a slightly positive / convex curvature in step (3), a state of substantially missing curvature (see in each case step (5) in Fig. 1A / 1B ).

If the curvature value is referred to at the beginning of the crystal growth of the III-N layer or directly after the deposition of the intermediate layer of the mask material (such as in Fig. 1 for example at step (3)) with "K _a " or "K _A " (K _beginning ) and the curvature value at a later time (such as in Fig. 1 at step (4)) and in particular towards the end of the growth of the III-N layer of the template (approximately according to Fig. 1 in step (5)) with "K _e " or "K _E " (K _end ), the curvature difference (K _a -K _e ) of the template, measured in each case at growth temperature, has a positive sign. Preferably, K _a -K _{e is} at least 5 km ^-1 , more preferably at least 10 km ^-1 . On the other hand, this curvature difference (K _a -K _e ) is preferably not too large; it should preferably not be greater than 50 km ^-1 , more preferably not greater than 20 km ^-1 .

By recognizing and actively influencing this behavior and related relationships, it is possible by the process of the present invention to produce a template comprising a first III-N layer which is not curved at epitaxial growth temperature, in any event is substantially non-curved (such as FIG for example in Fig. 1B Step (5)), or is negatively curved (such as in FIG Fig. 1A Stage (5) illustrated). Deposited by dashed lines, steps (5) and (6) represent the respective final states of the finished template, respectively at growth temperature (step (5)) and after cooling at room temperature (step (6)).

In a preferred embodiment of the present invention, all of the crystal growth steps described above in the first embodiment, including the optional nucleation step, are carried out via metal-organic vapor phase epitaxy (MOVPE). Alternatively or in combination, however, the crystal growth steps described above can also be carried out via HVPE.

When layer thicknesses of suitably at least 0.1 μm, for example in the range of 0.1-10 μm, preferably of 2-7.5 μm, of the III-N layer fabricated as described above are applied to the substrate, a template becomes according to the invention which is excellent as an initial template for reuse or processing for epitaxial growth of others Layers and in particular of other III-N layers is suitable and then the problem of tendency to cracking can be met, especially if subsequently grown much thicker III-N layers such as III-N solid crystals (ingots, boules) or deposited. Suitable techniques for growth or deposition of thicker III-N layers as III-N bulk crystals can be selected, for example, vapor phase epitaxy (vapor phase epitaxy VPE) - including, in particular, the hydride vapor phase epitaxy (HVPE), Ammonothermalverfahren, sublimation and the like.

Illustrates an exemplary course of the method according to the invention according to a possible embodiment Fig. 2 ,
The following parameters are plotted over time: the change in the growing surface (indicated by the decreasing amplitude of the reflectivity, in arbitrary units au in the lower part of the figure) and the temperature (ordinate left, upper line corresponding to process temperature, lower line corresponding to wafer temperature ) and the change in curvature (ordinate right) of the growth surface. The measurement of the curvature of the growth surface takes place in-situ, feasible with an EpicurveTT curvature measuring system of the company LayTec (Berlin, Germany), which makes it possible to simultaneously obtain data on the temperature, reflection and curvature of the growth surface.
Individual process steps or sections are in FIG. 2 specified. These have similar parallels to the representation in FIG. 1 , The sections that are in Fig. 2 denoted by "desorption" and "GaN nucleation" correspond to those in Fig. 1A / 1B designated stages (1) and (2) and thus to provide a sapphire substrate. Without distance or time delay and thus directly on nucleation (GaN or AlN nucleation; Fig. 1A Stage (3)), or close to it or after only a short (possibly very short) growth period (cf. Fig. 1B Step (3)), the intermediate layer is deposited with masking material as in Fig. 2 displayed. The portion designated by the term "GaN layer" corresponds to III-N epitaxial "crystal growth" according to steps (4) to (5) of Fig. 1 , In the course of the epitaxial III-N crystal growth following the interlayer deposition, the technical realization is recognizable that the curvature decreases from K _{A over} time until the end of the growth of the III-N (GaN) layer of the Templat which is about 20-30km ^-1 lower curvature K _E (compared to K _A ) is reached. Finally, it can be cooled to room temperature (cf. Fig. 1A / B stage (6)). With such a procedure, it becomes possible for the III-N (GaN) layer of the template to be substantially non-curved at the end at the growth temperature, ie, at a thickness in the order of a few μm; For example, the curvature value (K _E ) at epitaxial growth temperature can be in the range of a maximum of ± 30 km ^-1 , more preferably ± 20 km ^-1 to be zero. The procedure may, if desired, be varied so that at the end K _E is negative at growth temperature and thus the template has a convex curvature. After cooling to room temperature, the template shows a significantly increased convex curvature and thus a noticeable compressive strain. If this template at a desired time - about to grow a thick III-N solid crystal - heated again to growth temperature, the state is again achieved with essentially missing or alternatively negative curvature, which according to the surprising findings according to the invention an excellent basis for further epitaxial III-N growth with reduced tendency to cracking creates.

In Fig. 3 is a corresponding course (presentation and caption as in Fig. 2 indicated) on sapphire samples as starting substrates, if other than in Fig. 2 an intermediate layer of masking material is deposited much later (namely 300 nm). Although, unlike in the case of Fig. 2 in which the mask material intermediate layer was deposited at a very small distance of 15 nm, in the case of Fig. 3 a concave curvature (ie, K _A -K _E is <0). However, the execution also shows Fig. 3 in that, with a predetermined definition of the distance, the degree of curvature in the template obtained can be adjusted as desired. Accordingly, the template of Fig. 3 After cooling to room temperature a significantly lower convex curvature than the template of Fig. 2 , With regard to the avoidance of cracking during further epitaxial III-N growth, in particular with thicker III-N layers, the deposition of the intermediate masking material layer is at a very small distance (from about 0 nm to about 50 nm, cf. Fig. 2 with exemplary distance of 15 nm) strongly advantageous, here in comparison to the result after Fig. 3 at a distance of about 300 nm.

Fig. 4 schematically shows in a possible variant, the expected change in the curvature of the growth surface (right ordinate) and applied temperature (left ordinate, upper line corresponding process temperature, lower line corresponding to wafer temperature) for the case of a possible further embodiment of the present invention, optionally a deposition of an intermediate layer with mask material is combined with a reduction in the III-N growth temperature during the growth of the III-N layer of the template. In this possible and optional embodiment, after providing a sapphire foreign substrate, which also includes applying a very thin GaN or AlN nucleation layer (recognizable in the graphs in the sections of an initial high temperature followed by cryogenic phase), it is first heated again to growth temperature , Then possibly a - not shown here - Rekristallisationsphase connected, then as described above, an intermediate layer with Mask material to be deposited, which can be done as described, for example, at a time when already above 50 nm, or over 100 nm and or, for example, 300 nm thick III-N layer has grown. In addition and unlike the in Fig. 1 and 2 However, illustrated base embodiments will now, either simultaneously with this interlayer deposition or in a certain, preferably short period before or after a temperature drop (see Fig. 4 indicated temperature ramp of about 30 ° C after raising to growth temperature) and then the growth of the III-N layer of the template continued at this lowered temperature to obtain an additional contribution to curvature reduction. In the overall result of this combination, the curvature of the template at the growth surface is expected to decrease in the course of further growth, ie K _A -K _{E is} well above zero, as in principle in Fig. 4 illustrated.

As an alternative to lowering the temperature for continued growth of the III-N layer of the template, additional process parameters can be used to ensure compliance with the relationship K _A -K _E > 0.

Further possibilities and various embodiments for controlling curvature and / or stress in the III-N layer of the template, based on this at least one further III-N layer and optionally a thick solid crystal with a reduced tendency to crack on the template to apply are out Fig. 5A . 5B and 5C can be seen, wherein Figs. 5B and 5C still results to comparisons without interlayer included (each lines (B) and (E)). In Fig. 5A-C the bending behavior of the III-N layer of the template is plotted at growth temperature versus its thickness. Show Fig. 5A and 5B the section of the preparation of corresponding templates, wherein the MOVPE was used as an example as a growth technique, whereas Fig. 5C show a later section of the preparation of thicker III-N (here GaN) layers using these respective templates, using the growth technique of HVPE, which is particularly well suited for making thicker layers to Msssiv crystals.
The results show a consistent trend that the curvature is significantly affected by how the distance of a single interlayer of mask material from the sapphire starting substrate or an optional nucleation layer thereon is adjusted. It can be seen that in the experimental constellation used in the sapphire / GaN system used here, the condition K _a -K _e > 0 for the cases without distance (ie line "0nm") and for the cases of distances "15nm" and "30nm "certainly is fulfilled and obviously still for distances to about 50nm. At longer distances of greater than 50 nm, ie as shown at 60 nm, 90 nm and 300 nm, this condition is not primarily satisfied, but surprisingly the increase in curvature is comparatively strongly damped, with the result that such an increase can be kept smaller than in cases where no intermediate layer of masking material has been applied (cf. Figs. 5B and C Comparison lines (B) and (E)), and in particular when grown on a low-temperature deposited nucleation layer (LT-GaN nucl) (cf. Fig. 5 Covenant C, reference line (E)). The procedure of the invention shows the much better controllability of favorable template properties as well as the ability to tailor temple curvatures as desired, which can be used for further III-N epitaxial growth.

So confirmed Fig. 5A in that the provision of only an intermediate layer of mask material at a controlled distance from the starting sapphire substrate, optionally with an optional nucleation layer formed thereon, permits a very precise adjustment and control of a desired curvature value. Furthermore, it can be seen that, taking into account relevant factors such as the distance between the intermediate layer of mask material and the thickness of the grown III-N layer and thus the growth time, such a state can be set in the corresponding finished, substrate-bound III-N template, in which the template according to the alternative solution principle for preventing cracking at growth temperature is not or substantially not curved or is negatively curved, ie the curvature can be limited to at most 30km ^-1 , more preferably to at most 20km ^-1 or even better to at most 10km ^-1 , or preferably even to negative values is adjustable. In addition, as described, it is possible to further influence the difference with other process parameters such as temperature variations in the growth of the III-N layer of the template, and if desired, to ensure that the specific relationship K _A -K _E > 0 is maintained ,

The template obtained according to the invention has advantageous properties and features, which are further described below. As such, it is an interesting commercial item, but it may also be further processed directly thereafter or, alternatively, indirectly after provision, storage, or shipping, as a template in the context of further steps described below.

A template for producing further III-N single crystal according to the present invention is not curved or substantially not curved in the temperature range of epitaxial crystal growth, or it is negatively curved. For example, if the template used is sapphire of a thickness (d _sapphire ) of 430μm (approximately, ie ± 20μm) for the template and GaN of a thickness (d _GaN ) of 7μm (approximately dh ± 0.5μm) as the III-N crystal layer or is set, the expression "im essentially not curved "is preferably defined so that the curvature value (K _e ) at zero epitaxial growth temperature is within ± 30 km ^-1 , preferably within ± 10 km ^-1, around zero, the term" not curved "then means a K _e value about zero, eg
0 ± 5 km ^-1 and especially 0 ± 2 km ^-1 ; and the term "negatively curved" is then defined by a curvature at growth temperature in the range of below 0 km ^-1 , for example in the range to -150 km ^-1 , more preferably in the range of -25 to -75 km ^-1 .

It should be noted that when using III-N materials other than GaN, the exact curvature value may vary; but according to the invention it remains with the intended setting of a (substantially) non-curvature or a negative curvature. Further, in setting the other layer thicknesses of the curvature value may vary depending on the respective layer thicknesses in analogy to the following simplified Stoney's equation, according to which - if the film (d _III-N) is substantially thinner than the substrate (i.e. _{the substrate)} - the relation [wherein R = Radius of curvature and ε _xx = deformation ( strain )]: $$1/\mathrm{R}=6*\left({\mathrm{d}}_{\mathrm{III}-\mathrm{N}}/{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="imgf0001.png,imgf0004.png"\; state="\{\{state\}\}">d</figure-callout>}}^2{}_{\mathrm{substratum}}\right)*{\epsilon }_{\mathrm{xx}},$$

wobei im Fall der Wahl anderer Materialien diese Gleichung mit entsprechenden Werten d_Substrat/d_III-N berechnet wird.Assuming a very thin layer, ε _xx is assumed to be constant, ie if the layer thicknesses change, the system reacts with a change of R (the change of ε _xx resulting from a change of the curvature is neglected). Thus, when using the exemplary materials sapphire and GaN, but setting other than the aforementioned layer thicknesses (d _sapphire / d _GaN ), the curvature value depending on the respective layer thicknesses analogous to the Stoney equation in the following range: $${\mathrm{K}}_{\mathrm{T}\left(\mathrm{dgan};\mathrm{dSaphir}\right)}={\mathrm{K}}_{\mathrm{T}\left(7\mu \mathrm{m};430\mu \mathrm{m}\right)}\times {\left(430\mu \mathrm{m}/{\mathrm{<figure-callout\; id="2"\; label="d\; sapphire"\; filenames="imgf0001.png,imgf0004.png"\; state="\{\{state\}\}">d\; </figure-callout>}}_{\mathrm{sapphire}}\right)}^2\times \left({\mathrm{d}}_{\mathrm{GaN}}/7\mu \mathrm{m}\right).$$

where, in the case of the choice of other materials, this equation is calculated with corresponding values d _substrate / d _III-N .

For example, for a template according to the invention, this means that if a curvature of 250 km ^-1 exists for a 430 μm sapphire and a 3.5-4 μm thick GaN layer, a bend of 425 km for a 330 μm thick sapphire wafer occurs in the same process ^{. 1} results.

It should also be noted that the curvature at room temperature is altered as compared to the curvature at growth temperature, which may under certain circumstances be significantly altered. For example, when using sapphire as a foreign substrate, the template becomes due to plastic deformation during cooling from the growth temperature to room temperature, mainly due to the different thermal expansion coefficients of the different crystalline materials - In addition impressed (only generated by extrinsic compression) voltage. This should be in Fig. 1A and Fig. 1B with a state of the final stage (6) of the template according to the invention are schematically illustrated at room temperature, wherein in comparison to the final stage (5) at growth temperature in each case a significantly more negative curvature is present. Accordingly, in addition or alternatively, care is taken that, for example, in the case of the materials sapphire and GaN, the curvature at room temperature in the range of K _{T (7 μm, 430 μm)} <-200 km ^-1 , preferably -200 to -400 km ^-1 , is preferred in the range of -300 to -350 km ^-1 ; again referring to the simplified Stoney equation for cases of other layer thicknesses,
K _{T (dGaN; dSaphir)} = K _{T (7μm; 430μm)} x (430μm / d _sapphire ) ² x (d _GaN / 7μm).

In a further preferred embodiment, the template has a radius of curvature in the range from -4 to -6 m at room temperature for the case d _sapphire = 430 μm and d _GaN = 3.5 μm.

A further possibility to characteristically describe the product or structural properties of the template obtained according to the invention is possible by specifying the deformation of the lattice constant or the strain.

wobei a die tatsächliche Gitterkonstante im Kristall und a₀ die theoretisch ideale Gitterkonstante darstellt.The deformation ε _xx is defined as follows: $${\epsilon }_{\mathrm{XX}}=\frac{\mathrm{Lattice\; constant\; a}-{\mathrm{Lattice\; constant\; a}}_0}{{\mathrm{Lattice\; constant\; a}}_0}$$

where a represents the actual lattice constant in the crystal and a _{0 represents} the theoretically ideal lattice constant.

X-ray methods for the determination of absolute lattice constants are given in MA Moram and ME Vickers, Rep. Prog. Phys. 72, 036502 (2009 ) discussed in detail.

zunächst für die Gitterkonstante c aus einem 2Theta-Scan mit Drei-Achsen-Geometrie in symmetrischen Reflexen wie z.B. 004. Die ideale Gitterkonstante nach V. Darakchieva, B. Monemar, A. Usui, M. Saenger, M. Schubert, Journal of Crystal Growth 310 (2008) 959-965 ) beträgt c0= 5.18523±0.00002 Å. Die Bestimmung der Gitterkonstanten a erfolgt dann nach der ebenfalls z.B. in M. A. Moram and M. E. Vickers, Rep. Prog. Phys. 72 (2009) 036502 angegebenen Gleichung $$\frac{1}{d_{\mathit{hkl}}^2}=\frac{4}{3}\frac{h^2+k^2+\mathit{hk}}{a^2}+\frac{l^2}{c^2}$$

aus asymmetrischen Reflexen hkl wie z.B. -105 im 2Theta-scan. Als ideale Gitterkonstante a0 für unverspanntes GaN kann a0 = 3.18926±0.00004Å nach V. Darakchieva, B. Monemar, A. Usui, M. Saenger, M. Schubert, Journal of Crystal Growth 310 (2008) 959-965 ) angenommen werden. Zum Hintergrund der Phänomene intrinsische und extrinsische Spannung, u.a. unter Beachtung von Gitterkonstanten, vgl. Hearne et al., Appl.Physics Letters 74, 356-358 (2007 ).The determination is based on Bragg's law $$\mathit{n\lambda }=2d_{\mathit{hkl}}\sin \theta$$

first for the lattice constant c from a 2Theta scan with three-axis geometry in symmetric reflections such as 004. The ideal lattice constant after V. Darakchieva, B. Monemar, A. Usui, M. Saenger, M. Schubert, Journal of Crystal Growth 310 (2008) 959-965 ) c0 = 5.18523 ± 0.00002 Å. The determination of the lattice constants a then takes place according to the likewise eg MA Moram and ME Vickers, Rep. Prog. Phys. 72 (2009) 036502 given equation $$\frac{1}{{\mathrm{<figure-callout\; id="2"\; label="d\; hkl"\; filenames="imgf0001.png,imgf0004.png"\; state="\{\{state\}\}">d\; </figure-callout>}}_{\mathit{hkl}}^{\mathit{}}}=\frac{4}{3}\frac{{\mathrm{<figure-callout\; id="2"\; label="H"\; filenames="imgf0001.png,imgf0004.png"\; state="\{\{state\}\}">H</figure-callout>}}^2+{\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="imgf0001.png,imgf0004.png"\; state="\{\{state\}\}">k</figure-callout>}}^2+\mathit{hk}}{a^2}+\frac{l^2}{c^2}$$

from asymmetrical hkl like eg -105 in the 2Theta scan. As the ideal lattice constant a0 for unstrained GaN, a0 = 3.18926 ± 0.00004 Å after V. Darakchieva, B. Monemar, A. Usui, M. Saenger, M. Schubert, Journal of Crystal Growth 310 (2008) 959-965 ). On the background of the phenomena intrinsic and extrinsic stress, taking into account lattice constants, cf. Hearne et al., Appl. Physics Letters 74, 356-358 (2007 ).

wobei M_f das biaxiale Elastizitätsmodul bedeutet. Die Bestimmung der Verspannung σ_xx ist durch Ramanspektroskopie einfach möglich, z.B. wie in I. Ahmad, M. Holtz, N. N. Faleev, and H. Temkin, J. Appl. Phys. 95, 1692 (2004 ) beschrieben; dort wird das biaxiale Elastizitätsmodul 362 GPa als Wert aus der Literatur herangezogen, wobei ein sehr ähnlicher Wert von 359 GPa aus J. Shen, S. Johnston, S. Shang, T. Anderson, J. Cryst. Growth 6 (2002) 240 zu entnehmen ist; somit ist ein Wert für das biaxiale Elastizitätsmodul M_f von etwa 360 GPa passend und konsistent.Furthermore, the properties can also be specified by the strain σ _xx , where $${\sigma }_{\mathrm{xx}}={\mathrm{M}}_{\mathrm{f}}\cdot {\epsilon }_{\mathrm{XX}}$$

where M _{f is} the biaxial modulus of elasticity. The determination of the strain σ _xx is easily possible by Raman spectroscopy, eg as in I. Ahmad, M. Holtz, NN Faleev, and H. Temkin, J. Appl. Phys. 95, 1692 (2004 ); There, the biaxial modulus of elasticity 362 GPa is taken as the value from the literature, with a very similar value of 359 GPa J. Shen, S. Johnston, S. Shang, T. Anderson, J. Cryst. Growth 6 (2002) 240 it can be seen; thus, a value for the biaxial elastic modulus M _f of about 360 GPa is appropriate and consistent.

In the temperature range of an epitaxial crystal growth, a template according to the present invention has a value ε _xx ≦ 0 (ie including ε _xx = 0), but in particular ε _xx <0. This value can be determined directly from an in-situ measurement of the curvature.

In addition to the presence of an intermediate layer with mask material, a template according to the present invention may further have a compressive stress of σ _xx <-0.70 GPa at room temperature, and / or the deformation ε _{xx of} the template at room temperature may be in the range of ε _xx <0, preferably in the range 0> ε _xx ≥ -0.003, more preferably in the range -0.0015≥ ε _xx ≥ -0.0025 (or -0.0015> ε _xx ≥ -0.0025), and especially in the range -0.0020 ≥ ε _xx ≥ -0.0025.

A suitable curvature measuring device that can be used in conjunction with a gas phase epitaxy system is, for example, the curvature measuring device of Laytec AG, Seesener Strasse, Berlin Germany (cf. DE102005023302A1 and EP000002299236A1 ). These curvature measuring devices work well with available gas phase epitaxy equipment, such as the MOVPE, HVPE or MBE (Molecular Beam Epitxy) also combine and enable temperature measurement at the wafer surface.

Accordingly, after epitaxial crystal growth, a template is obtained which, due to the properties described above, is suitable for producing crystals of special quality and with special features in further epitaxial growth steps. The template according to the invention is thus outstandingly suitable for further use, that is to say it can be provided as such, temporarily stored or sent for further use, or it can be used further directly in an overall process.

• aa) Bereitstellen eines Templats, welches ein Saphir umfassendes Startsubstrat und mindestens eine III-N-Kristallschicht umfasst, wobei das Startsubstrat und die mindestens eine III-N-Kristallschicht so gebildet sind, dass das Templat im Temperaturbereich eines epitaxialen Kristallwachstums keine oder annähernd keine Krümmung aufweist oder eine negative Krümmung aufweist, und
• bb) Durchführen eines epitaxialen Kristallwachstums zum Bilden von weiterem III-N-Kristall auf dem Templat gemäß aa), wahlweise zum Herstellen eines III-N-Massivkristalls,
• cc) optional Trennen von III-N-Einkristall oder III-N-Massivkristall und Fremdsubstrat.

A further subject of the present invention provides a process for the preparation of III-N single crystals, wherein III means at least one element of the third main group of the Periodic Table, selected from Al, Ga and In, the process comprising the following steps:

• aa) providing a template which comprises a sapphire-comprising starting substrate and at least one III-N crystal layer, wherein the starting substrate and the at least one III-N crystal layer are formed so that the template in the temperature range of epitaxial crystal growth no or almost no curvature has or has a negative curvature, and
• bb) carrying out an epitaxial crystal growth to form further III-N crystal on the template according to aa), optionally for producing a III-N solid crystal,
• cc) optionally separating III-N single crystal or III-N solid crystal and foreign substrate.

This object of the invention is based on the alternative solution principle to minimize or completely suppress the risk of cracking by the conditions defined in steps aa) and bb).
In a preferred embodiment, the template provided in step aa) comprises the above-described intermediate layer with mask material, in which respect reference may be made to the above description for forming the template having such an intermediate layer. However, in this subject matter of the invention according to the alternative solution principle, such an intermediate layer need not necessarily be present, because the curvature state defined in step aa) can alternatively be adjusted by other conditions, especially by appropriate temperature control and variation during III-N growth of the Templats, as also described elsewhere.

Due to the imprinting of lattice deformation and compressive stress according to the present invention, the state of the template provided in step aa) can also be defined by the growth-temperature of the III-N crystal of the template being ε _xx ≤ 0 (ie including ε _xx = 0), but in particular has an ε _xx value of <0, the value preferably in the range of 0> ε _xx > -0.0006 and more preferably in the range of -0.0003> ε _xx > -0.0006 lies. At room temperature, a compressive stress of σ _xx <-0.70 GPa may be present. The deformation ε _xx at room temperature of the template according to the invention preferably has a value in the range 0> ε _xx ≥ -0.003, more preferably in the range -0.0015≥ ε _xx ≥ -0.0025 (or -0.0015> ε _xx ≥ - 0.0025) and in particular in the range -0.0020 ≥ ε _xx ≥ -0.0025.

Thus, in a further embodiment of the present invention, III-N single crystals can be prepared which are obtained by - without or with interruption between steps aa) and bb) - additional epitaxial crystal growth on the template obtained according to the invention for forming further III-N crystal is performed. Further epitaxial III-N crystal growth can be carried out at a growth temperature that can be chosen independently of the aforementioned crystal growth temperatures.

Other conditions of further crystal growth on the template are now freely selectable. Thus, III-N materials can be grown whose III component can be chosen and varied as desired. Accordingly, at least one (possibly further) GaN, AlN, AlGaN, InN, InGaN, AlInN or AlInGaN layer (s) can be applied to produce correspondingly thicker III-N layers or III-N single crystals , Preferably, both the III-N crystal layer of the template and the epitaxially grown III-N crystal form a purely binary system, e.g. GaN, AlN or InN, or the III-N crystal layer of the template is a binary system, especially GaN (at least mainly because the nucleation layer may optionally be of a different material, such as AlN), and III-N epitaxially grown thereon Crystal is a freely selectable binary or ternary III-N material, in particular binary GaN.

Step bb) may immediately follow step aa), alternatively the process may be interrupted therebetween. It is possible to change the reactor between steps, which in turn allows the growth of III-N crystals in step bb) via a different growth method than was used in the preparation of the template provided after step aa) to obtain the respective steps to select optimal conditions. Thus, the additional epitaxial crystal growth on the template prepared according to the invention is preferably carried out by HVPE. The favorable choice of step bb) under HVPE conditions allows high growth rates and, correspondingly, the achievement of thicker layers. However, it is also possible to carry out all the steps of the process involving the entire growth, including the formation of temples and the subsequent deposition of the further epitaxial III-N layer, in a single plant with a specific growth technique, for example only by means of HVPE, so that the Steps aa) and bb) are carried out in the same reactor.

According to the invention, in the process for producing III-N single crystals according to the above-described embodiments, epitaxial crystal growth can be performed on the template provided, so that after completion of the epitaxial growth with significantly reduced risk of cracking, thick III-N single crystals of very good crystal quality with layer thicknesses of at least 1 mm, preferably of at least 5 mm, more preferably of at least 7 mm, and most preferably of at least 1 cm. Due to the freedom from cracking, the entire thickness of the solid crystal can advantageously be utilized.

After completion of the epitaxial crystal growth to prepare a III-N single crystal, the crack-free III-N single crystal may optionally be separated from the substrate (optional step cc)). This is done in a preferred embodiment by self-detachment, such as when cooling from a crystal growth temperature. In another embodiment, the separation of III-N single crystal and the substrate may be accomplished by abrading, sawing or a lift-off process.

If the epitaxially grown III-N single crystal has a sufficiently large thickness to obtain a so-called III-N boule or intrin, it is possible to singulate this single crystal by suitable methods of forming a plurality of individual thin slices (wafers) , The singulation of the single crystals includes common methods for cutting or sawing III-N single crystals. The wafers thus obtained are outstandingly suitable as a basis for the production of semiconductor devices and components, for example optoelectronic or electronic components. Thus, the wafers produced according to the invention are suitable for use as power components, high-frequency components, light-emitting diodes and lasers.

In all process stages, in particular in the actual, epitaxially grown III-N layers of a III-N boule or -gine and correspondingly in the III-N single crystal for the resulting wafers, the inclusion of dopants is possible. Suitable dopants include n- and p-type dopants and may include elements selected from the group consisting of Be, Mg, Si, Ge, Sn, Pb. Se and Te. For semi-insulating material, suitable dopants may include elements selected from the group consisting of C, Fe, Mn and Cr.

In a further preferred embodiment, the crack-free III-N single crystal of gallium nitride is composed, and this crystal has a lattice constant a in the growth direction in the range of < a ₀ , in particular in the range of 0.31829 nm < a ≤ 0.318926 nm. As a reference value of the lattice constant a ₀ of GaN, the value a ₀ = 0.318926 nm can be assumed here (cf. V. Darakchieva, B. Monemar, A. Usui, M. Saenger, M. Schubert, Journal of Crystal Growth 310 (2008) 959-965 ). This corresponds approximately to a lattice constant c in the range of 0 ≤ ε _zz <+0.0001.

Examples example 1

As a growth technique, an MOVPE on pretreated sapphire (which is subjected to desorption and nucleation) is used with the details given below. The temperatures mentioned here refer to the nominal set temperature of the heaters; the temperature at the template or crystal is deeper, sometimes lower by about 70 K (cf. Fig. 2 and 3 : here the heater temperature is shown with the upper line and the measured temperature of the wafer with the lower line).

Reactor:

MOVPE Aixtron 200/4 RF-S reactor , single wafer, horizontal

Foreign substrate:

C-plane sapphire substrate, off-cut 0.2 ° in m-direction
430 μm thickness
unstructured

Desorption step (Fig. 1 (1); 100)

• Reactor pressure: 100 mbar
• Heating: From 400 ° C to 1200 ° C in 7 min
• Reactor temperature: 1200 ° C
• Process temperature duration: 10 min in H ₂ atmosphere
• Cool to 960 ° C

Nucleation step (Fig. 1 (2); 101)

• Gas flows: 25 sccm trimethylaluminum (TMAl), bubbler: 5 ° C, 250 sccm NH ₃
• Cool to 960 ° C
• Opening the valves
• Nucleation: 10 min
• Increase of ammonia flow to 1.6 slm

T-ramp; if necessary, crystal growth (FIG. 1 (2) to (3); 103)

• Heating from 960 ° C to 1100 ° C in 40 sec
• Reactor pressure: 150 mbar, H ₂ atmosphere
• Gas streams: optionally 16-26 sccm of trimethylgallium (TMGa), 2475 sccm of NH ₃
• Crystal growth time: 0 - 10 min (corresponding to 0-300 nm)

SiN deposition (Fig. 1 (3); 102)

• Gas flows :: 0.113 μmol / min silane, 1475sccm NH3
• No TMGa
• Pressure: 150 mbar
• Temp: 1100 ° C
• Duration: 3 min

further crystal growth: (Fig. 1 (4); 104)

• 1100 ° C
• Reactor pressure: 150 mbar, H ₂ atmosphere
• Gas flows: 26 sccm TMGa, 2000 sccm NH ₃
• Crystal growth time 90-240 min, corresponding to 3-10 μm GaN thickness

Growth end and cooling: (Fig. 1 (5) - (6))

• Switch off heating and TMGa power
• Reduction of NH ₃ : 2000 sccm to 500 sccm in 40 sec
• Shutdown: NH ₃ flow below 700 ° C
• Switch: NH ₃ stream to N ₂ stream

Fig. 5A shows the course of the curvature at growth temperature (1350 ° K), plotted against the thickness of the grown GaN layer and thus over time, differentiated depending on the distance SiN (Si _x N _y ) versus the AlN nucleation layer. The zero point here refers to the beginning of the continued growth of the III-N layer 104A, 104B (ie after step (3) and before or at step (4) in FIG Fig. 1A / 1B ) The curvature behavior can be specifically and precisely controlled. Table 1 below gives the in situ, ie measured at growth temperature ε _xx values and measured at room temperature curvature values C (km ^-1 ) and the determined over C ε _xx values at room temperature towards the end of the template production with respective thicknesses by approx. 7μm again. Table 1 Distance AlN and SiN Thickness (μm) ε in-situ C @ RT (km ^-1 ) ε @ RT 0 nm 7.21 -6,00E-04 -396 -2,27E-03 15 nm 7.09 -4,50E-04 -365 -2,13E-03 30 nm 6.76 -4,00E-04 -367 -2,24E-03 60 nm 6.73 1,10E-04 -298 -1,83E-03 90 nm 6.81 1.00E-04 -299 -1,82E-03 300 nm 7.29 2,50E-04 -293 -1,66E-03

Example 2 and Comparative Examples

On selected templates prepared according to Example 1, in which GaN layers with SiN intermediate layers directly on the nucleation layer (sample A, not according to the invention) or after very small (15-30 nm, sample D) or larger (300 nm, sample C; not according to the invention), or according to comparative examples in which GaN had grown without SiN (Sample B) or on low-temperature GaN nucleation layer (Sample E), the curvature was followed analogously to Example 1, namely in the range of MOVPE growth until about 7μm as in Fig. 5B shown, or in the implementation of further HVPE growth to about 25μm as in Fig. 5C shown. The results of Figures 5B and 5C again show the significantly better result in terms of setting and behavior of the curvature of the template (A), (C) and (D) according to the invention in comparison to the comparison templates (B) and (E) without SiN intermediate layer.

Further comparative examples

In other comparative examples, similar experimental conditions can again be used, except that no intermediate layer of masking material is deposited.

Fig. 6 shows typical in situ data of MOVPE growth from GaN to sapphire in another Comparative example, wherein in the lower graph, the development of the curvature during the process for three different sapphire substrates is shown (see. Brunner et al. in J. Crystal Growth 298, 202-206 (2007 )). The arrows refer to the curvature values K _A and K _E to be read. With a curvature K _A of 50 km ^-1 and a curvature K _E : of 70 km ^-1 here K _A -K _E <0, ie the GaN layer is intrinsically tensilely tensed at growth temperature. By cooling, this strain of the GaN layer is superimposed on an extrinsically compressive strain.

Claims (15)

1. A process for preparing a template comprising a substrate and at least one III-N crystal layer, wherein III denotes at least one element of the main group III of the periodic table of the elements, selected from Al, Ga and In, wherein the process comprises the steps of
   providing a foreign substrate comprising sapphire, and growing a crystalline III-N material on the substrate, wherein a mask material is deposited as interlayer in the crystalline III-N material at a distance from the foreign substrate, which optionally exhibits a III-N nucleation layer, and subsequently the growth of a crystalline III-N material is continued, and wherein the mask material is deposited in situ in the same reactor during the preparation of the template within the III-N-layer of the template, wherein the distance of the interlayer of the mask material to the foreign substrate or respectively the III-N nucleation layer optionally formed thereon is at most 50 nm,
   wherein during the crystal growth a curvature difference of K_a-K_e ≥ 0 is adjusted, wherein the curvature of the growth surface of the III-N crystal at a first, relatively earlier time point is denoted as K_a and at a second, relatively later time point is denoted as K_e.
2. The process according to claim 1, characterized in that the curvature difference (K_a-K_e) is at least 5 km^-1, preferably at least 10 km^-1, more preferably at least 20 km^-1 and in particular at least 50 km^-1.
3. The process according to claim 1 or 2, wherein the template is further used for depositing one or multiple further III-N crystal layer(s), optionally for producing III-N bulk crystal, wherein the III-N crystal layer(s) or the III-N bulk crystal comprises epitaxially grown GaN, AlN, AlGaN, InN, InGaN, AlInN or AlInGaN crystals.
4. The process according to claim 1 for producing a III-N single crystal, wherein the process comprises the following additional steps:

   carrying out an epitaxial crystal growth for forming further III-N crystal, optionally for producing III-N bulk crystal on the template, and

   optionally separating III-N single crystal or III-N bulk crystal and foreign substrate.
5. The process according to claim 4, wherein a mask material is deposited as interlayer in the provided template in the region above the starting substrate in the III-N crystal layer of the template, such that a distance of the interlayer of the mask material to the foreign substrate or respectively the III-N nucleation layer optionally formed thereon is at most 50 nm, wherein preferably the mask material is deposited in situ in the same reactor during the preparation of the template, and the III-N- growth process is continued directly after the deposition of the mask material.
6. The process according to one of the preceding claims, characterized in that when for the template as substrate sapphire with a thickness (d_sapphire) of approximately 430 µm (i.e. ±20 µm) and as III-N crystal layer GaN with a thickness (d_GaN) of approximately 7 µm (i.e. ±0.5 µm) is used or set, the III-N crystal a curvature of the template (K_T) at the growth surface

   (i) at growth temperature is specified in the range from 0 to -150 km^-1, preferably in the range from -25 to -75 km^-1, and/or

   (ii) at room temperature is specified in the range of < -200 km^-1, preferably from -200 to -400 km^-1, more preferably in the range from -300 to -350 km^-1;

   wherein when using or setting different layer thicknesses (d_sapphire/d_GaN) the curvature value lies depending on the respective layer thicknesses analogous to the Stoney equation in the following range: $${\mathrm{K}}_{\mathrm{T}\left(\mathrm{dGaN};\mathrm{dsapphire}\right)}={\mathrm{K}}_{\mathrm{T}\left(7\mu \mathrm{m};430\mu \mathrm{m}\right)}\times {\left(430\mu \mathrm{m}/{\mathrm{d}}_{\mathrm{sapphire}}\right)}^2\times \left({\mathrm{d}}_{\mathrm{GaN}}/7\mu \mathrm{m}\right),$$

   

   if the film d_GaN is substantially thinner compared to the substrate and ε_xx is considered as constant,
   and/or wherein a compressive stress is produced within the III-N-material, and preferably the III-N single crystal of the template exhibits a compressive stress σ_xx of < -0.70 GPa at room temperature,
   wherein ε_xx is determined by an X-ray measurement of the absolute lattice constant.
7. The process according to one of the preceding claims, wherein the interlayer of the mask material is deposited at a set maximum distance from the substrate, or respectively from the III-N nucleation layer optionally formed thereon, of maximally 50 nm, and/or wherein the mask material is a material on which a III-N deposition is inhibited or prevented, preferably the mask material is selected from the group consisting of Si_xN_y and in particular Si₃N₄, TiN, Al_XO_Y and in particular Al₂O₃, Si_XO_Y and in particular SiO₂, WSi, and WSiN, wherein x and y respectively independently from each other denote positive numbers which lead to respective stoichiometric or non-stoichiometric compounds of SiN, AlO and SiO, respectively.
8. The process according to one of the preceding claims, characterized in that the substrate consists of sapphire.
9. The process according to one of the preceding claims, characterized in that the curvature of the III-N crystal of the template is additionally changed in at least one growth phase by carrying out a deposition at a lowered growth temperature compared to that of a preceding deposition stage of III-N material of the template.
10. A process for preparing III-N crystal wafers, wherein III denotes at least one element of the main group III of the periodic table of the elements, selected from the group of Al, Ga and In, wherein the process comprises the following steps:

    a) carrying out a process according to one of the claims 3 to 9 for forming a III-N bulk crystal, and

    b) separating of the bulk crystal for forming wafers.
11. A template with a substrate comprising sapphire and at least one III-N crystal layer, wherein III denotes at least one element of the main group III of the periodic table of the elements, selected from the group of Al, Ga and In, wherein in the region above the foreign substrate in the III-N crystal layer of the template a mask material is provided as interlayer, wherein the III-N crystal layer of the template is defined by one or both of the following values (i)/(ii) of the deformation ε_xx:

    (i) at room temperature the ε_xx value lies in the range of <0,

    (ii) at growth temperature the ε_xx value lies in the range of ε_xx ≤ 0,

    wherein ε_xx is determined by an X-ray measurement of the absolute lattice constant,
    wherein the distance of the interlayer of the mask material to the foreign substrate or respectively the III-N nucleation layer optionally formed thereon is at most 50 nm.
12. The template according to claim 11, wherein, if for the template as substrate sapphire with a thickness (d_sapphire) of approximately 430 µm (i.e. ±20 µm) and as III-N crystal layer of GaN with a thickness (d_GaN) of approximately 7 µm (i.e. ±0.5 µm) is used or set, wherein ε_xx is determined by an X-ray measurement of the absolute lattice constant,
    the III-N crystal a curvature of the template (K_T)

    (i) at growth temperature is specified in the range from 0 to -150 km^-1, preferably in the range from -25 to -75 km^-1; and/or

    (ii) at room temperature is specified in the range from -200 to -400 km^-1, preferably in the range from -300 to -400 km^-1,

    wherein a negative curvature is a convex curvature,
    wherein when using or setting other layer thicknesses (d_sapphire/d_GaN), the curvature value lies in the following range depending on the respective layer thicknesses analogous to the Stoney equation: $${\mathrm{K}}_{\mathrm{T}\left(\mathrm{dGaN};\mathrm{dsapphire}\right)}={\mathrm{K}}_{\mathrm{T}\left(7\mu \mathrm{m};430\mu \mathrm{m}\right)}\times {\left(430\mu \mathrm{m}/{\mathrm{d}}_{\mathrm{sapphire}}\right)}^2\times \left({\mathrm{d}}_{\mathrm{GaN}}/7\mu \mathrm{m}\right),$$

    

    if the film (d_GaN) is substantially thinner compared to the substrate (d_sapphire), and ε_xx is assumed to be constant.
13. Use of a template according to one of the claims 11 or 12 for producing thicker III-N layers or III-N crystal boules or respectively III-N bulk crystals, which optionally thereafter are separated into individual III-N wafers, or use of a template according to one of the claims 11 to 12 respectively for producing semiconductor devices, electronic or opto-electronic devices.
14. Use of a mask material as interlayer in a template which exhibits a substrate comprising sapphire and a III-N crystal layer, wherein III denotes at least one element of the main group III of the periodic table of the elements, selected from the group of Al, Ga and In, for controlling a curvature value and/or a stress of the template to deposit at least one further III-N crystal layer on the substrate after setting of a particular curvature value and/or a particular stress, wherein a distance of the interlayer of the mask material to the foreign substrate or respectively the III-N nucleation layer optionally formed thereon is present and is at most 50 nm.
15. Process for the production of semiconductor devices, electronic or opto-electronic devices, for which the process for the production of III-N crystal wafers according to claim 10 is carried out.

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